First I suggest that you read the Double Degree Dilemma essay posted under the "Read Me’ thread closer to the top of this forum. Second, I always add the option of doing a BA in music or a BA in something else entirely, and continuing music through lessons and extracurricular performance. Many schools give credit for both as well.
There is no need to know her major or career goals yet. She can decide at the end of her sophomore year after exploring.
If she goes the BA route, she should submit a music supplement with recording/video, music resume, and letters of recommendation from music teacher and/or director (two is fine). These supplements can indeed increase chances for acceptance at top schools.
Attendance at conservatory prep programs also seem to increase chances. MSM is very well respected. To the other poster, no need to change programs due to “prestige”, but if there is a problem with a teacher or classes only offered at Juilliard, those might be reasons for change. I would stick with MSM.
Harvard is moving away from the traditional classical curriculum, or, rather, diversifying it so that music concentrators who haven’t done years of conservatory prep don’t suffer. Just fyi. However, in past years it seems conservatory prep students have high admit rates.
Oberlin has enhanced their music BA, in their Musical Studies major, with increased access to the Conservatory. Otherwise, for a kid who is not doing a BM, it can be better to avoid schools with a conservatory or school of music, because the best teachers and opportunities go to the BM students (this may also include some state U’s). There are exceptions.
Tufts, Williams, Amherst, Vassar, Clark, are all schools with good music programs. There are many many more. Bard requires a double degree of conservatory students but look into resources for BA students in terms of music.
Many young people don’t know what they want, and many change their ideas for a major (and a career). I think having some time to explore is really healthy. Your daughter sounds like a hard worker and that is respected everywhere.