@WWWard , re the 2300 SAT student, that isn’t uncommon. Those stories appear each April on this site. Totally agree that sub 20% acceptance rate colleges are reaches for all. Also agree that EA or ED is a great idea. Nothing relieves stress like an early acceptance.
17 is far too many, IMO. If the student likes the safeties, I think two or three are fine. Your D did get into a match, and that’s great. Matches aren’t sure things. Impossible to know why she didn’t get into the other four, but she applied to enough schools to ensure she got into at least one she was happy about. But wow, what a lot of work that must have been. Even ten apps is a lot of work. And as somone said earlier, finding the match and safeties is hard work too. It’s easy to find reaches.
OP, this is all useful info for your sister. It’s important or her to be realistic and honest about her stats when the time comes.