The most important thing is that she plays something she likes. Playing one style or another because it's easier is silly if that's not the music you want to make. If someone gave me a piano but told me the only thing I'd ever be able to play on it was hip-hop, I'd sell the piano.
Don't discourage her from Scruggs style picking if that's what she expects banjo music to sound like. The classic advice holds true -- start slowly, concentrate on playing clean albeit slow, and in a few weeks she can have a couple of tunes friends will recognize. Maybe not FMB or Dear Old Dixie, but Yankee Doodle, Buffalo Gals, and Goodnight Ladies can all be learned pretty quickly to some recognizable degree.
Give her someone to play along with, that's the best help you can offer.