She doesn’t need competitions. Juilliard precollege and whatever other distinctions are just fine. Has she done any summer programs? As long as she plays well, and submits a supplement with recording/video, music resume, and music letters or recommendation, her chance of admission may be enhanced. it depends on various things, like what the school needs, other applicants, and so on but many of us know kids who got into reach schools based on that supplement. And you do not have to be a music major for that either.
Be aware that Harvard and a few other schools have changed their curriculum for music in order to address more diverse backgrounds and interests. You can read about it on their music dept. site or google it.