The offset on the 5 series is different than the 3 series so the 3 series wheels will not fit unless you use big spacers.

the wheels from the 7 series are close and will fit if the tires are not oversized.
there is a great deal of good 5 series info here. just run the search feature.

http://forums.bimmerforums.com/forum/forumdisplay.php?f=201


Also the weakest point on that car is the Auto Trans. If the car has over 125k miles on the car and the transmission fuild has never been changed I would avise her to start saving for a rebuild. It will be at least 2500 to fix.