For starters, welcome to MTBR.
Second, I would like a bit more info on the buyer.
So your girlfriend wants to buy a bike, hey?
Yes
First off, what type of riding does she do? Trail? Pathway? XC? Downhill? Free Ride?
Trail/Road (mostly trail)
How much experience does she have?
Only 6 months or so
How aggressive is she?
2-4 days ~2/3hours (more on weekends)
Has she test riden them? If not, have her ride them, see how they feel under her.
She liked the Rockhopper better as it was Lighter when we test rode them
Fit is all. If she doesn't like how it feels, she won't ride it...
We can talk about differences in the bikes later...
Now just a little info for you. Don't rush things around here. People will see your post when they see it. They will be quite happy to help you out, just relax... Ride, have fun!