My daughter attends Barnard, but never attended any such summer programs. However, given our proximity to the city, she audited two different-subject classes on (two?) different dates to get a sense of the college in operation, how differently college classes are conducted in general, and what professors/students were like. It was time well spent and her HS allowed such days-off.
May I suggest you add the tags for “Barnard” and “Brown” to the topic “tags” of your post, as it will become more visible to people getting notified who have subscribed to those two topics.
Also, consider asking your question in the current “class of…” or “early admission” threads for those colleges, as some of the young women discussing their own admission chances/outcomes may have attended these programs themselves.