How can I stop from becoming a Revenge of the Bridesmaid Girl?

So I have this friend. She is a very close friend, she is going to be a bridesmaid in my future wedding and I am currently her bridesmaid. Anyways, so last October me and her were out for a drink or two and dancing at a bar when a guy hit on her and got her number. So then like two weeks later this guy became her boyfriend. About two and a half months later he took on another title and the wedding planning started. Anyways, since they started dating I have not had one minute alone with casey other then one night and he texted her the whole time we were out about how he wished she was there and how he hadn't seen her in like two weeks or something. *rolls eyes* So everytime its the three of us (which is anytime I try to hang out with her) he starts a fight with her, or gets angry about this or that. So she has told me countless times that she just wants to go away us girls. I want to give her that but he is smothering her so bad. He gets mad at her for the stupidest things. Oh I almost forgot, he is jealous of people who my friend once dated. He is very clingy which is going to work great with him being in the navy. And neither of them have every lived on their own. Neither one of them every had to have their own budget. And I just don't know what I should do. I hate seeing her sad, I hate seeing her feel uncomfortable, I hate watching her ask me to save her from her family and wedding planning and her boy too. I love her lots and I don't know if she feels trapped in the wedding because so much has been planned and money has been put in. So I would love to hear what you guys think of the situation.