well im not gonna b as optimistic as lc3606, because i was a lot like carly. everyone was enthusiastic about my abilities except 4 me, i was told i could've been a child prodigy, however practicing was never a major priority with me until just this past year when i actually got excited about playing, and that had 2 come from me. no amount of encouragement from anyone could make me want to practise if i didn't feel like it.
the best thing u can do really is what Ic3606 has already said, just try 2 pick out pieces that will get her excited about piano. good luck