I am afraid that this is an effort in futility to try to give the OP advice, in order to help and protect her daughter, when the OP's own viewpoints and beliefs continue to contribute to the problem....
What exactly do you want me to do?
Stop answering the phone?
Make her get a job and give up the internship?
Go down and kidnap her and make her move home?
Tell her brothers not to look out for her?
I do want and expect her to be independent. And she always has been. He pays for the roof over her head but she is not dependent on that roof. She does not need him to do anything for her at this point nor will she after graduation. He is paying for it but she doesn't need it. There is a huge difference in needing someone to support you or help support you and having options at all times. One of the differences in her and the women he has dated is that she doesn't "need" him to do anything. Her objective is to graduate and get a job as a personal trainer. Her objective is to use her knowledge in that to help broaden the business that her and her brother have. Her ultimate goal is to own her own gym. She hasn't lost her sight on her goals. I can't fault him for making this a priority as it is one for her too. It is their priority.
We have talked at length about abuse and the signs. We have talked about why his ex saw things the way she did or why she said the things she did. And I will keep that dialogue open with her. We have talked about how hard marriage is at any age and how it changes, how each of you change. How what you love about him now, you will hate in a year.
He did say we should let him mom plan a cheap wedding. Its not going to happen. We have come to the agreement to put it on hold for a little while. I agree with the fact that he is quick to run to his mom. But I can't change that all I can do is guide dd to see it for herself. I have to be careful not to put her on the defensive about him because that will stop all conversations about him. I don't want to do that.
I can listen to the things that make her angry and tell her to "just pack up and come home" which is only going to make her mad or I can listen and guide her to make a choice of what she should do. The former turns off the dialogue, the latter keeps it open. And seeing it for herself is the ticket to her making the right choice. We have even had the conversation that at some point they will have an argument that is big enough that she will pack up and come home. Maybe for an hour, maybe a day, maybe a week and maybe for good. But when that happens, we are there if she wants to talk and we are there just to be there for her.
When I say her brother looks out for her, I don't mean he follows her around like a body guard. I mean he watches and listens and makes sure all is well. He doesn't let anyone take advantage of her and he does talk to her about it to show her what to watch out for. He is guiding her in this business. And it is a cut throat business, so his guidance is needed. He does give his opinion of things the bf says or does but honestly she takes it a little different from him. And if someone along the way tried to hurt her, I am sure they would have to answer to him but that isn't likely to happen.
I can sit here and say we made a grave mistake by not fighting her on moving in with him. But then were would we be right now? She would still be where she is, she would feel like she couldn't just tell us if something was wrong and she would feel like she really doesn't have options. That isn't better. And that is why we made the choice we made. She is 19 years old, as hard as it is, she is an adult.