Didn't I just say that it was the GATEWAY INSTRUMENT?
Meaning: teach her piano because it's generic enough to lead her into something cooler and easy enough that a young child (8-10 yrs old) would have no trouble beginning. It's also a nice generic instrument that helps you wrap your ears around pitches and the way things should sound. Tuning, rhythm, etc...
Also, you have to learn to read both treble and bass clef. So... bass player in the making perhaps?
Not to mention the sheer accessibility. You can take piano in a lot of middle schools now. IT WOULD BE HOMEWORK FOR HER TO JAM WITH YOU.