I just got a Wii yesterday. So far it's pretty darn cool.
Easy menus and a nice clean look.
The Wiimote takes a little getting use to. It is very sensitive and hard to control when trying to click on little buttons on-screen. I got it mostly for my 4 year old daughter as there weren't a lot of kid games for the PS3. After about 10 minutes of frustration with the controller she caught on and is having loads of fun!
I see most games are $50. To me, that's a lot but there are cheaper ones out there. If it's worth it is another story though. It all really depends on how you like the game.

dark_orb
On a side note you might want to look into getting her De Blob, I played a pc demo of it and it was great fun.