Whatever you don, dont bring her for a dinner at Hooters .
Dont give her a GF1 too. That way, she will become GF2.
But seriously, how about an evening picnic? Find a nice shoreline (Marina Barrage has a nice view) and just camp out, some light finger food and enjoy the view. An expensive dinner is also great, but that will just divert more resources from the next lens upgrade.
Hooters? I just had dinner with a gal at hooters a couple of days ago really. She loved it and was the one who suggested it. So really depends on the gal, if u can't guess what she wants, perhaps the best gift to her is to get to know her better.