She’s better off happy and alone than miserable and married to a loser.

Treating one child better or worse than another is unjustifiable in 99% of cases. I’m not talking about garden-variety variations, where parents are slightly closer to one child because of common interests, but don’t give that child unearned privileges just because they like baseball. I’m talking about purposefully excluding a child out of spite and refusing to repair the rocky relationship. 

It’s common for kids and parents to go through stages where they’re more or less emotionally close to one another. Still, it’s the parents’ responsibility to try to make it so their kids at least feel comfortable approaching them when they’re in distress or need support. There’s a big difference between a teenager self-isolating because they’re at the age where they don’t want to tell their mom everything, and a young adult never telling their parents anything because they can’t trust them, as they have shown time and time again that they don’t care or support them in the life they have created for themselves.