The two of you started with a 102-point difference. Probably her credit profile "needed" some new, clean accounts, so her score didn't drop. Your credit profile didn't, so your score dropped.
Same thing happened when my youngest got her second CC. In fact, her scores increased.
* Credit is a wonderful servant, but a terrible master. * Who's the boss --you or your credit?
FICO's: EQ 781 - TU 793 - EX 779 (from PSECU) - Done credit hunting; having fun with credit gardening. - EQ 590 on 5/14/2007