I did see Roland's mom as being kinda helpless...helpless in the face of Broadcloak's sexual dominance of her. (even though Flagg did state later that she retained some kind of inner defiance of him...I forget what he said exactly) Perhaps I'm extrapolating, but it seemed to me that she loved her husband and loved her son but Marten "forced" her to cheat on her husband with him and be distant to Roland. This was my impression. (it's still unclear to me how he pulled that off...magic of some sort? It appears so to me)

With Susan, I got the message that she felt like she didn't have a choice or rather, not much of a choice. It was pimp herself out or live in poverty. Seems that a lot of women, in the absence of a better option, might make such a deal and once that better option did come along she might have felt that she couldn't do anything about it. On the other hand, maybe she was just stupid...but no one said you had to be smart to be a damsel in distress.