Ikaruga, Bayonetta, Eternal Sonata, Mirror's Edge, UNO, Might & Magic: Clash of Heroes, Castle Crashers, Guardian Heroes, Insanely Twisted Shadow Planet, Pinball FX2, Castlevania HD, Castlevania Symphony of the Night, Dorito's Crash Course (Free!!) and Boom Boom Rocket are all games I thoroughly enjoyed.
Edit: Actually, Insanely Twisted Shadow Planet is a really good game for "beginners"; it's not too hard and it is a really rewarding experience to figure out stuff in it. Dunno if it's worth 15 dollars to you/her, since it's really short. It's really steep for this game, but as said, the experience and atmosphere of the game are just amazing.
If she does get it, tell her she should add me so we can play the multiplayer (both DLC and non-DLC) together. :3