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Reading between the lines I see a mother with a large agenda of her own: "pushed the private ballet and piano lessons", "forcing... lessons she hates", "I wish my own mother had forced me".
Why is the LW forcing another person to do anything at all? In my book, that's a very poor way to live life. Certainly we have an obligation to impose on our children to, say, not drive cars at 13, but piano lessons are not in the same life-threatening category. I also doubt the importance of continuing both in making music a career; it is as if the LW has a very limited view of what a musical life might be.
In summary, it's time to start letting go and allowing this new-forming person to have beliefs, desires and goals of her own.