My daughter showed real interest in the piano and we were pushed by a high level Russian method school to start her at lessons before she was 3.5 but we didn't and then they pushed again around her 4th bday and we thought we should so we started. She participated in a concert at 5 and again at 7 and was slated to do the American protoge competition at 8 but she hit the wall and started to hate the piano. I backed off, got another teacher for a year, who wanted to push, so I found another, a jazz musician and he it taking a totally different approach and now she is seriously composing and finding her love of music again. I tell this story because doing piano or violin or cello at a high level requires serious commitment these days. There are too many parents pushing. Her friend, who plays the violin practices at least 2 hours a day weekedays, 4-5 hours weekend days. Plus she takes piano lessons on the side. And she is not good enough for American Protoge, which is the level you kind of need for Ivys to be impressed these days.
I recommend the harp. It is a different type of instrument but expensive.
If your daughter really likes it, then I think you should consider a better school and get her evaluated. Perfect pitch, etc to see how much she wants it and wants to apply herself.
We pushed in the beginning because we thought we should but she didn't love it enough. In hindsight, DD likes the fact she did those concerts but doesn't want to go back to it. But she will sit and work on compositions now, going over chords, writing the notes. So in the long run it worked.
Also, a good school will allow recitals all the time. DD's Russian school had a recital you join every Sunday afternoon. 10 kids would play any Sunday and so each time you mastered a couple of pieces, you could go play them for an audience. It was a good way before moving on.