Here are some guidelines for video editing:
CPU: Go Intel. Period.
If all she is doing are simple edits for short 5 minute or less videos, then all that is really 'required' is a simple i3 processor. My wife does little videos of our kiddo and we have a nice little 1080p camera, and her i3 is more than enough to do simple real time editing. But we are talking about simple cuts, with the occasional tital, nothing too outlandish or complicated.
If we are talking about doing hevily compressed 1080p video with lots of cuts, fades, transitions, and other such things then get an i5. An i5 can do just about anything.
If we are talking about video editing becoming her job, or there is potential that she becomes an enthusiest, then get an i7. The only real performance difference between an i5 and i7 will be in your export time for the final render. If she is doing a large volume of videos, then it becomes important to have as fast of an export time as possible, but we are only talking a 25-30% improvement between the two.
Storage: The single most important part of a video editor
You should have 2 parts to your storage strategy.
1) OS, Programs, and Scratch disc. This NEEDS to be on an SSD. Windows + Adobe creative suite + Office takes ~60GB of space. Then you need to have another 40GB for your scratch disc and export space. And lets not forget that you never want to fill a drive past the 80% mark, and you want some added cushen space for your most used documents, music etc (because really, this rig will not ONLY be for video editing). This means that you need a minimum of 240GB of SSD space, and more if you have a lot of other programs (like games) that take up a lot of space.
2) Bulk Storage. This is where you put big files, everything from your system backup, to movies you download/watch, to raw footage, to your final projects. 1TB is considered a minimum, and may fill up quickly due to the system backup and just normal file storage. 2TB is suggested, and would last a little while, while 3TB would be nice, but is realalistically overkill for someone who is just starting out because you will replace your HDDs every 5 years (because you plan on replacing them BEFORE they die), and as a hobbiest it would be difficult to fill your first 3TB that quickly, and 5 years down the road there will be much larger drives available that you can upgrade to.
While not required, I would HIGHLY recommend having a RAID array for your bulk storage. Drives die, and never when it is convenient, so it is good to have some active protection in the form of a RAID1 array. That way, if one drive fails, you simply replace it. The onboard Intel RAID is wonderful in that when a drive fails you still have full access to the working drive, and when you replace the old drive it does all of the copy work in the background so you do not have to wait forever to rebuild the array. I lost a drive last year, and was very thankful that I had that RAID1 in place. It was rather unexpected, and I would have lost some irreplaceable footage of my kiddo, as well as client footage for projects I have done over the years that are too big to back up on optical media.
Note that the bulk storage drives do not need to be very fast, just big and reliable. WD 'Green' drives are fast enough, though I like Seagate drives better. 7200RPM drives would be a little more responsive, but we are not talking about massive performance differences here.
Graphics: What you see is what you get.
Truth be told there is a lot of confusion out there about graphics and video editing. So let me simplify it for you:
GRAPHICS DO NOT MATTER. period, end of line.
Video programs simply do not use the GPU for much of anything. If you happen to get software that can use the GPU (like Adobe Premiere which can use CUDA), you will quickly find that it only uses that GPU support for very specific things, and for a hobbiest it will really not be for much. Personally I use the CUDA support all the time, but it is because I am a stickler for color correction, and Premiere has some great CUDA accelerated color correction features, and when doing color correction on top of titles and other things, then that extra CUDA kick helps a bit. But outside of that I have yet to use CUDA for anything else.
Just starting out the Intel HD4000 integrated graphics is simply good enough, and if she gets into things that will use the GPU later, then you can always purchase a good GPU down the road.
RAM: Super Important.
RAM is the life-blood of a video editing system, and as it is dirt cheap you should not skimp out on it. Get a minimum of 16GB in a 2x8GB kit. So far I have only had one project that has used 16GB of ram, and in it I had over 10 hours of raw footage, and I was editing a music video as part of the project which had a lot of things which rendered in RAM. If you can fit 32GB of ram in the budget then go for it. She may never need it, but it is cheap, and it is better to have it than not.
Note that the speed of the RAM really does not matter. Even 1333 will be able to put the bottleneck of the system onto an overclocked i7. Personally I would look at getting some stock 1600 and call it a day.
Overclocking and Cooling: Because you know you want to
First Cooling, because it is paramount.
Cooling for an editing rig has little to do with temperatures, and everything to do with how quiet you can make the system. As a part of video comes audio, and if she is editing some delicate bit of audio with the noise of a rig in the background, then there is a good chance she may miss something important when played back on a TV which has no fans, and (lets be honest) TV speakers will make audio mistakes readily apparent when even nice editing speakers/headphones may downplay it.
-Case: Look for a nice tight case that will take 140mm or larger fans. The smallest fan in your rig should be 120mm. As a general rule of thumb get the least amount of fans required to keep your system relatively cool. If you are not OCing, and do not have a monster GPU, then you can get away with a single intake fan, a single CPU fan, and then a PSU fan. If you are OCing then you may want 2 CPU fans, plus an additional case exhaust fan. Make sure all fans move air in a single direction (front to back and/or bottom to top) with as few obstructions in the way as possible. I have taken to adding foam padding (supplied by my local fabric shop... that was an akward conversation lol) as it will deaden some of the system noise. Higher end cases will have this already, which is nice.
Personally I have 1 120mm fan on front blowing in over my HDDs (I have 6 drives... so cooling is a must), 1 140mm intake at the bottom, 140mm PSU fan, modified GTX570 with 2 96mm fans, Hyper212 Evo with 2 120mm fans on the CPU, and then 2 140mm exhaust fans on top. All of the fans (except the CPU and PSU) are on a fan controller, and all of them run at ~800rpm. None of them move a lot of air, but they are all super quiet so the only noise I hear are the whine of the HDDs... which should be much quieter when my new HDDs come next week and I can consolidate down to 2 HDDs instead of my current 4 HDDs (+2 SSDs, but they don't make noise).
Overclocking is easy to do, and I highly suggest it to a point. With current Sandy and Ivy Bridge CPUs you should be able to hit 4.2GHz on any i5 or i7 with no problem, but there are some basic things you need in order to do it:
1) CPU cooler. A simple Hyper 212 Evo is good enough, and they are dirt cheap. If the stock fan is too noisy then they are easy to replace with some good quality fans that are quieter, and the EVO (unlike the +) comes with the mounting brackets to add a 2nd fan, which is a nice feature. If you are going for looks, then there are definitely some better options, especially by Zalman, but you pay extra for it.
2) OC capable motherboard. Get a z77 motherboard, preferably of an ASUS design, but ASRock has some good offerings as well and is a little cheaper (and is what I use).
3) OC capable CPU. What nobody talks about is that every i5 and i7 is capable of overclocking, but just limited to a max OC of 4.2GHz (4.5 if you are brave and mess with the BLCK which is not suggested), and limited to a Turbo OC rather than a set clock speed. Truth be told, 4.2 GHz is pretty damn good, and most unlocked processors can only hit a max OC of 4.5 to 4.7, so you are not missing much. If you do want to go past 4.2GHz, or want a set speed rather than relying on Turbo boost and thermal limiting, then you will need a K series processor (2500K, 2600K, 2700K, 3570K, or 3770K). When you are ready to OC then come back to the forums. It is pretty straight forward, but there is a bit more than I can go into right now.
Power: Because those who have power are better than those who do not.
In all seriousness, power is not a huge deal anymore. There is a huge race between AMD and nVidia to get the most performance per Watt these days, and so there is no longer any reason to get an oversized power supply. Even a 750W PSU is enough to drive 2 high end GPUs, and something in the 450-500W would probably be overkill for her setup.
There are however some very important things to look for.
1) Reliability. PC Power and Cooling make some of the quietest, most accurate, and longest lasting power supplies on the market, and being bought by OCZ has not changed that. Corsair, Antec, and Seasonic also make great devices. OCZ is more hit and miss, but their good PSUs are excelent, and their bad ones are quite terrible, so be sure to read reviews before buying (I love mine though).
2) Efficiency. Gold and platinum are perhaps overkill, and tend to be extremely expensive. Bronze and Silver are great, and do not cost a premium. 80 Plus (no color) should be avoided unless you are looking at a small PSU in the 250-350W range.
3) Noise. Typically look for a PSU with a single large fan. Minimum of 120mm, but preferably larger. Higher end fans have an option to operate with the fan off which is a nice option as it will run silent unless you are really pushing the system.
Audio: 9/10th of video is audio.
And it is so true! At the very least you should get a system with optical audio, and then go find a decent quality used stereo amp on craigslist that has an optical input. The clarity is nothing short of heart-stopping. digital audio is a little bit 'dead' so you may want to invest in some software such as Creative's xFi MB2 software to breathe some life back into it, but digital audio is the way to go.
Good speakers are hard to come by (I ended up building mine because there were no good ones in my price range), but thankfully good headphones are relatively cheap. I use some Sennheiser eH150 headphones which can be found for less than $100. They are not jaw-dropping, but they are great entry level studio headphones. There are better, but you pay for them.
Just stay away from crap like Beats Audio. Beats Audio is great for rap music and movies with explosions... but nothing else. When reading reviews on headphones look for ones that have good clarity, and an accurate sound reproduction rather than 'good bass'. Studio headphones will not give 'good bass', but the audio will be true to life, which is what you want to edit with.
If you want some decent speakers, then go into a Guitar Center and have a nice long chat with the people in their audio department. They have a wealth of knowledge, and most of the ones I have been in are good at finding the best option within your budget rather than constantly trying to upsell you into something 'better'. Plus they have all sorts of cool stuff to look at and drool all over
And Finally:
Form Factor: Because a rig does not need to be a monster anymore!
Seriously, I am designing some mobile editing rigs for a group I do tech support for, and I am amazed at what you can cram in a small box these days. You do not need the big sprawling full ATX tower anymore to do editing. If you are willing to sacrifice on the number of drives, and the ability to OC, you can fit an i7 with a duel slot GPU inside of a nice little ITX case with no problems whatsoever.
That being said, an ATX rig is easier to install and work on, and easier to shut up as well, but if you guys are young and still moving around a lot, then seriously consider a smaller rig. She may be less intimidated by it as well. If it were not for the number of HDDs I need in my system I would gladly trade my big CM690 for a much smaller compact rig that I can hide behind the desk somewhere.
I will follow-up with a build or two for you to use as a guideline.