Did the computer ever work properly?
If it did, then there are only two things that could of happen. She has either went to a site that has downloaded something to cause this problem or she let someone else use her computer who thought they knew more then they did.
Did she add any new software, or is it still set up as she brought it?
I know you said there are problems downloading, can you get another Browser loaded? If you can from either on line or disk then you could pin point whether IE7 is the problem. Then uninstall IE7, and do a clean install. Has she install any IE7 browser extensions or addons?
I know you are trying to be a friend, but with such a new computer, it must still be under some kind of warranty. I would let her take it back to Best Buy and let them do whatever they can. Seems strange that they can not do anything at the store she brought it at. Kind of what a Geek Squad was suppoed to do.
Other than that you could always wipe the HDD and reinstall everything. How much of a friend are you?
EDIT: Damn, I type slow.