Daughter had unhappy High School experience, should she not mention this during Rush?

[Pirouette]

Never bring-up anything negative about yourself during recruitment.
Shy is not a bad thing, but if your daughter wants to stand-out, she will need to at least good at making conversation. Sorority girls wont remember a girl just because she's pretty, we remember girls because we had a great conversation with them. Practice small talk, a lot.
And your daughter seems to have been very involved in high school. Volunteer work, activities/sports, and still making good grades is something to bring-up.
I didn't date a lot and I really did not "party" in high school. But that didn't stop me from getting a bid to a wonderful organization (that was considered a "top" sorority at my school when I went through recruitment).
Good luck to your daughter!