If she likes shooters, Quake 2 or 3 would be good because there are a lot of maps available that are small enough for 1 vs 1 play. If you go with Quake 2, look for a couple of maps called 2am and wasted.
If she'd rather play co-op missions instead of 1 vs 1, Rogue Spear would be a good choice that would run great on that GF2 card.
I can't comment on anything other than shooters, since that's about all I play.