I'm really curious to know how many Giant Bomb users have never even played games like Maniac Mansion, Day of The Tentacle, or Fate of Atlantis. Give the age of these titles, I bet it's a huge percentage and that is just so unfortunate.
Well, considering Maniac Mansion was released when I was two-years-old...
The first game I remember ever seeing, Super Mario Land, was released here when I was -2!
Portal 2, if she likes puzzles. Do the PixelJunk games have co-op? Those are pretty simple. Something like Terraria might be fun, also. Classic Nintendo platformers often have co-op; Super Mario World, Donkey Kong Country.