Wow! I've been in your shoes so many times. You must be really confused at all these different suggestions. Believe it or not most of them are very good advice.
The only problem is you need a mac genius to put them in order for you, by priority and likely relevance; This is what I do when taking my dog to the vet. Unfortunately, for us both, my superpower is bargain shopping, but I'll try to contribute a little something.
If you zap the pram (perammiter ram, misspelled/no charge) it couldn't hurt, although for the kind of performance issues you have I doubt it will be a miracle.
To do this, restart and when you see the screen go black hold down the p and the r and the option and command keys all at the same time while the start up cycles through with 3 separate start up cycle chimes ( I've been known to do 5 cycles, but I'm knutts)
Next the predictable thing to do with any performance mystery, assuming you have the boot-up or install disk for her OS, (you should always name the version OS X aka Snow Leopard/10.6 or leopard/10.5, etc.) is run Disk first aid, rarely fixes it or even identifies real problems but it's like centering your core.
Insert install disk (#1) ~link to a genius giving directions
(http://manuals.info.apple.com/en_US/macbook_13inch_mid2010_ug.pdf)
Select the icon on the left margin that represents your gf's Mac. Once it is highlighted select "repair permissions" ( I have been told to do this before selecting "repair disk").
You will see "verify permissions", "verify disk", above these choices, but I just select the bottom action buttons because it takes as much time to be told you need to repair permissions, and why not just do it.
Each step: "repair permissions" and "repair disk" can take 2-12 minutes or even more, so relax and don't worry, a watch pot never boils.
When you come back you can look at the log and see if permissions were whack, ( they usually are, at east a few) and then when you, concurrently, select "repair disk" and come back, if repairs were made, you see it in the scroll down log.
After these two steps, Go back to "Start up disk" in Utilities and choose the original icon representing gf's hard drive, and highlight it again, then select restart.
I know this seems daunting but if you drink the Apple coolaid, it's like changing your babies (that looks just like you) diaper, and becomes second nature. The steps above, and the next one, should be done periodically, to prevent the software from getting corrupted, (natural softwear and tear).
my final suggestion, (they're coming to take me away) A good cache cleaning is in order. Fresh off the press and free is
http://www.piriform.com/mac/ccleaner install it if you need to and then run it.
At this point if the problems isn't fixed, you may get advised to do other things and perhaps they are valid, but personally, even if i didn't have my mac backed up (everyone is saying Nooo!) I would reinstall the OS from that same "boot disk".
I say this because for a long time I sat on the same problem and didn't have a back-up drive or the space on my hard drive to partition, nor the confidence that i knew how, until I finally just reinstalled any way, devil may care, and never lost a font or a phone number. I may be wrong but that's my humble wanna be experience.
Mozl Tov!