hmmm....
For plays, musicals and concerts, check out
www.esplanade.com.sg
There's a listing and lots of info.
If you want something unique - you can try taking her up the world's largest tethered hot-air balloon ride, haha...
http://www.visitsingapore.com/publish/s ... lloon.html
But you only get to be up there about 15 mins or so.
For great wining and dining, you can try Michaelangelo's at Holland Village. They have a REALLY extensive list of great wines and the food is pretty good. My man and I were there for our first anniversary and got the best table in the house! We had called in advance, and they reserved it for us. They also gave us a lovely tiramisu dessert when we told them it was our anniversary! Service was excellent.
http://singapore.menulog.com/michelangelos/
I hope that helped!