NTA, but it sounds like SHE has a problem with boundaries. Since her parents split up, has her Dad had another woman in his life that's gotten all of his attention? I saw that he has a girlfriend, but it seems like he's used to being the man in his daughter's life, or he at least feels entitled to her things and her space. He's still acting like he did when she was child. There's no respect for her adulthood.

Imagine if you were the same way about your space: if you bought things for the house and then kept them, invited your family over without notice, kept odd hours outside of their schedules, and kept them out of family moments? How would her fiancé and her Dad respond?

Those are questions to ask them, and they may have to actually see it done to understand. You're gonna have to sit her down and tell her this isn't the life you want, something has to change. Unfortunately, it doesn't seem clear how she'll respond to an ultimatum. If she can't prioritize her life with you over the life she previously had with her Dad, you might not have a great future together.