I noticed that whenever I unplug my sister's i mac (while it's off) it disconnects the keyboard (according to her)?Better how? Some keyboards have a tiny delay on bluetooth and of course there is battery life to think about. The Apple keyboard does not seem to have any issues being use wirelessly though. In general wired is the best option, wireless for convenience or some look that people try to go for. If you are going to get one anyway or already have it, just see if there is any difference you can tell.
I noticed that whenever I unplug my sister's i mac (while it's off) it disconnects the keyboard (according to her)?
shouldn't it connect automatically after being plugged in and turned on?Not sure what you mean there, if the computer is off, the keyboard is of course not working. Disconnects how exactly? Your original post does not really have anything to do with this other question/issue.
shouldn't it connect automatically after being plugged in and turned on?