I am an old coot now, never having married and never had the chance to have a girl (autism works that way) but I am wicked smart as Tenthunter can attest to and I would treat her (your daughter) right. But at this point I won't try to rob the cradle. Tell her though to stick to her guns and insist before any intimacy that she has his ring on her finger. It seems to be a sad commentary on society today that the idea for the guy to sample the milk (sex) without paying for the cow (marriage) is all too common. She needs to probe and learn to test his core values and push him on commitment. The best marriages are covenant relationships and do not rely on emotion to try to tie it together. Emotions come and go, but sticking through the hard times, when you don't feel like it and treating your husband or wife with respect, kindness, gentleness, mercy, and grace are always in front of you.
Hope this helps her. But it sucks getting such a cad......