AKG K167
Sennheiser HD25/Amperior
Sennheiser Momentum
ATH M-50
I know from those that theyve got good bass.
I currently own a pair of HD25, but I wouldnt recommend them for your GF because the clamping force will probably annoy her. I've ordered a pair of MDR-1R; from what I read, it's very comfortable and produces good sound (Jude said best sub $500 closed-cans). But I'm not sure if the bass will "wow" her, as some said that the bass is not as boomy or punchy. Besides, the MDR-1R look great IMO
(they're in a black/red version and white/silver/brown edition, I ordered the black/red one, the red looks mighty on the black)
Main reason why I'm stepping off the HD25 is due to the sibilance.
I could've picked the Momentum, but they're more expensive and the design of the headphone makes it look huge on my head. AKG K167, I heard it's a bit fragile.
My mate owns a pair of ATH-M50's, the bass and comfort is good but I (personally) don't really like the design.
If she's only using it for @home use (with an amp, small one like a fiio e11 would do), I'd say get her a pair of HE-400