I highly recommend this Admissions Preview event (officially known as “Women in STEM at Caltech”) for high school girls who are interested in Caltech. I just attended with my DD’16. The event is all day, and provided a much more intimate and less intimidating view of the Caltech experience for women. The content is excellent and inspiring, (e.g. current faculty keynote speaker, female student engineering panel, JPL panel, typical admissions/financial aid info and tour, a super sit-down lunch!, and much more.) For families who are considering a future west coast or CA tour of colleges in the summer months, I recommend you try to plan around this annual event (typically in August). Good luck to all as you support your student in the college process!
Woohoo! Glad you guys had a blast 
Since it seems like your daughter and you had such a positive experience, I would strongly advise her to jot down some notes about her most memorable moments during the event along with some general thoughts about Caltech. When I was applying to Caltech, I responded to the “Why Caltech?” question by describing my enthusiasm for the culture there and included plenty of thoughts that had gone through my head while I was visiting as a prospective student. It really helps admissions see that the applicant understands/likes the student culture to some degree and cares about the school! Of course, my words are merely suggestions, and your daughter has her own writing style. Either way, good luck!