“The Dean” has answered this question a gazillion times but each response may be slightly different than the one that preceded it because it really depends on the student herself. In this case, from what you’ve told me about your daughter, I suggest that she NOT disclose her ADHD to her target colleges.
Why? Well, in a perfect world, colleges wouldn’t discriminate against an applicant with any sort of disability (in fact, they’re not allowed to). But colleges also do not have to reveal their reasons behind a denial, and I believe that discrimination is out there, whether the college folks own up to it or not.