Ugh, Buttercup, I am sorry you have to deal with this. My mother was the same way, and in the end I just told her what my boundaries were and told her if she violated them I would stop all contact with her for a set period of time. Some of those boundaries were I did not want to see my father under any circumstances and I did not want that issue to be discussed at all (it was absolutely not negotiable). She did violate those boundaries, so I stopped all contact with her for three months. When I resumed contact again she was much better behaved. :P

Denial can be SUCH a hard thing for 'non-offending' parents to break through (I say that in inverted commas because a mother that is aware of abuse and not only allows it to continue but puts forth her children for abuse so she herself can escape it IS offending in my book). One day my mother pitifully cried to me "But it can't be true, because if it is how will I be able to sleep with him again?" My mother is rather pathetic, and I feel pity for her more than anything.

What I came to understand was that my mother doesn't accept it because she CAN'T. For whatever reason in her own personal make up she is incapable of making that leap from protecting her own interests to protecting those of her children and grandchildren. She loves us deeply - I know she does - but her need to protect her own world runs deeper. My own personal belief is that facing the truth would mean facing her own part in the abuse of myself and my siblings (knowing and allowing it to continue). I simply don't think she is emotionally strong enough to face that.

I don't know why your own mother can't face the truth, but I would wager that she has her own very good reasons for denial continuing to have a bigger pay off for her. Whatever her reasons are, if SHE isn't going to protect you you certainly have every right to take steps to protect yourself. You don't have to convince her of anything or change her mind about anything, but you CAN set limits for what you will put up with and what you won't stand for. You are in the 'right' here, and you actually have a lot of power - much more than you realise!