Is my brother in law being controlled by his girlfriend?

My brother in law met his girlfriend at work, they are both accountants. They started dating when she was 24 and he was 29. At first she was really quiet when she would come over. She doesn't have any friends, and would mainly be on her phone at gatherings. Since day one, she attached herself to my BIL, needing him to pay attention to her at all times. To the point where at the dinner table, he would be kissing her and holding her hand. At Thanksgiving, people were really uncomfortable how they were behaving.

She gave my BIL an ultimatum that it was her or his best friend of 10 years. She didn't like his best friend, they broke up, then he chose her. She didn't want him around us either, it's been over a year. She prefers to have him all to herself, they will go weeks without leaving the house. She has managed to deceive my in laws to portray herself as innocent. Yet, she calls my BIL gay, names, says she can't be with him then tells him he can't see anyone.

I could go on about everything that has happened the past 3 years, I don't want to write a book.

I have said in the past she is controlling and my husband says the same thing. My BIL now says he wants to marry her, she's immature, along with holds a grudge forever.