I am in the minority in thinking perhaps Marolyn made the best decision she could for her kids. In California, you don't get full custody unless you can prove abuse.  M being a drunk would not have been sufficient for her to get full custody. I am certain they would have ended up with 50/50 custody. That is how it works I have seen more than my share of California divorces. If she went to a lawyer, and learned this, what would be the best decision? To leave, and leave them with him, alone, half their lives? I actually think, it was better for her to stay with the kids and love them and be there. If we see anything about this woman from our far away vantage point we see she is absolutely devoted to those kids. I think, in her mind, staying may have been better for them. I don't think it is realistic to think she could have pulled the children from Prem's influence. I think her only way of doing that would have been to flee into hiding. That is more easily said than done. I also think, I really do, that the way Prem talks about the kids that if she had tried to take them he might have pulled an "OJ". I think she would very realistically fear for her safety if she left him. I for one can't say she made the wrong choice. She was really trapped. But now that they are adults? Maybe she could leave, or maybe she is just too broken. 

Just my speculation...