Find a teacher who can instill the motivation in her to play. One thing I always regret is that none of my teachers had instilled that kind of love, the motivation for me (which is why I'm such a horrible player right now and why I gave up for many years). Then again, not everybody has the love for classical music that is required to have that kind of motivation. Then again, the piano is a more versatile instrument

twisted

so classical music isn't the only type she can learn to love.
While the piano is "easier" to learn and to teach oneself, if one wants to properly learn how to play it, lessons are pretty much essential.
Edit: I probably forgot to mention that the best way to make your daughter motivated (well, it was for my renewed interest in the violin) is to have her listen to good recordings. Recordings that make her want to play those pieces. Rachmaninoff, Tchaikovsky, and Brahms will be good starts, but make her understand that she's probably years of hard work away from even attempting those works :lol: