To be clear, I’m not saying that her MT talent doesn’t strengthen her application. It definitely does. She’s impressive at something, and that makes her stand out as someone colleges might like to add to their student community.
I just think it’s important to draw a distinction between that and actually being recruited. The athletic equivalent of this situation is an athlete - talented enough to play on a college team, but doesn’t want to play in college. Schools will still see her talent and her work ethic, and say, “This student is impressive, and we like having impressive students on our campus.” But they will not say, “Oooh, we need this athlete for our low-performing club team.” That just isn’t how club teams work.
And many a sports parent, when the decision is made that their child won’t be a recruited athlete, has said exactly what you’re saying: “I was hoping all of those hours she has put into it would be worth something.” It still is worth something - both because they loved it and it helped make them who they are, and because it does make them stand out in the applicant pool. It just doesn’t rise to the level of recruitment, or being a “hook.” Is it a “boost?” Well, that’s a more vague term. In the sense that it does strengthen her application, I think it’s fair to call it a boost. It’s just hard to quantify. And when a student gets in or doesn’t, you can never know how much one factor mattered.
Good luck with the search!