She did what?

Gosh, what does one do when a friend/family member is walking into a reeeealy bad decision? I guess nothing huh? Worst part is she knows its bad but is doing it anyways and when it all falls apart, she'll expect to be rescused, like some deliberate damsel in distress. You see, one of my SILs is going to be marry the father of her baby. The same worthless guy who has cheated on her CONSISTANTLY, who put her out on the side of a TX highway at midnight WHILE she was pregnant cuz he got mad at her for telling him to slow down (oh he was driving drunk too), who has never bought the child anything, same guy who gave her a dreadful disease-the kind that never goes away, who has disrespected everyone in her family, who joined the military and refused to claim his daughter so she could get medical benefits, who she has tried to move in with before and it lasted a whole 3 days before he kicked her and his kid out....shall I go on? I could. And after all the abuse and neglect shes actually going to marry him and move to TN. Seems just like a few weeks ago she was calling me all upset cuz he got caught cheating again. How am I supposed to react? Its a joke. If I congratulate it, its like I am condoning it. If I say nothing or how I feel, then I am a "hater". I just don't get it....