Well it all really depends on what your gf is into.
I've played countless coop games with my gf on PS3 ie. LBP, Street Fighter, Portal, Lego,Rayman, Resident Evil...and she didn't really enjoy them as much except for Resident Evil. Resident Evil 5 was her fav coop game (When the demo came out we played the hell out of it over and over again, also she enjoyed the game so much she helped me platinum it), she also liked RE6 too but she preferred RE5 cuz she just liked to stay as one character). So, I'd give RE5 a try, but all depends on ur gf's taste as well.
Honestly, playing Portal coop drunk will not help, you'll be stuck forever but hella fun!! (from experience lol)







