Please do your girlfriend a favor and DON'T do what I see a million FG riders doing - riding an ill-fitted bike. Put all that 650 vs. 700 wheel size/frame size aside for a second and consider ALL things to get a bike fitted correctly - seat, stem length and height, seatpost height, crank length, handlebar width/drop, etc. A good place to start, so at least you're not shooting into the wind, would be to get her measurements and start inputting the numbers here:
http://www.competitivecyclist.com/za...LCULATOR_INTRO
That should help you get started.