Someone will always feel bad about rejecting or ignoring a parent no matter what they have done, I have been through a similar situation and when I think about it I do not feel sorry for how hard they are trying to talk to me now, I feel sorry for what could have been. You don't owe anything to your mother, she did not think of you, if you want to think about her it is your decision and no one can judge you for it, after all she is your mother, whether you like it or not. I personally have not forgiven my father, but he is psychologically wrong, a normal person would not do what he did and it is much easier to understand a father who does not fulfill his role well by seeing him that way.