It is worrying. And thank goodness your cousin has such a support group looking out for her. But as was said above what the boyfriend is doing may not be manipulative.

There are plenty a ways a 20 yr old can by emotionally immature without having been born of an alcoholic birth mother. I'm not saying what is going on isn't a disaster. I'm not saying this boy won't bring your cousin down. I'm saying he may be just as naive and erratic as she is and they're feeding off one another. No one understands them like they do each other. Everyone is treating them like children. We are living breathing Romeo and Juilet

I think Alice's mom and dad should really get to know fiance's grandmother. Feel her out. See what she has to say on the matter. Is she disfunctional herself and will shut you out? Or is she just a flake who is too used to getting walked all over but still knows they're being stupid kids?

Alice needs people who she knows will be in her corner. She's rebelling and grieving. If you push, she will pull. She will welcome a friend and shun an overbearing parent. If/when this all falls apart she needs to know there are people who she won't think will tell her "told you so" because all they did was harp on her in the beginning. If she and her fiance have isolated her from her support group she will have the option of staying because she has the misguided belief that she has no one to turn to or she could run to the people who were there for her throughout it all even if they didn't agree they supported her.

I did all this and wasn't developmentally disabled. I was just a young, stupid, victim with too much pride for my own good. I feel for her parents, you, and your family. I grew out of it, you fear she never will and I can't imagine that worry for the rest of your lives.