It depends on what she wants to do after college. The ivy alumni network you have access to is a very real and valuable commodity as you pointed out in your original post. However, that commodity is only valuable in some sectors. I’d take a hard look at this and go from there. My BIL went to Harvard and (because I have college bound kids) we talk about this a lot. If she’s certain to go get a masters or PhD I’d do unc for free, get kick ass grades and get into the best grad school for her field. If she’s going into the workforce right after college I’d pick the ivy (especially if it’s finance or consulting).
My caveat is that if she feels that the fit at one or the other is better and that one school is her people and she’d be super happy there. Go there.