Well, while I would not advocate making choices in high school based on college admissions, recruiting does seem to be on your mind. So I will just add to the discussion here and say that playing the harp will help her way more than any sport, with admissions. She can do a recording, a music resume, and get some recommendations from a teacher or director and submit it to colleges.
I think a lot of kids stick with sports for social reasons. I always admire the outliers who leave sports to do something else.
Has she entirely stopped with music? Does she take lessons? Perform?
One of mine unexpectedly switched from sports to music and is in a doctoral program in music now.