Girl I'm sorry you were yet again let down by your Mother, but remember anyone can have a child it takes a special person to actually BE a Mother! You've been lucky to have had your step Mom in your life even if it was cut short that is really something many don't have a second chance at having a Mom. Plus you've been the Mother to your children you never had and that is awesome! You are awesome!
Some people just don't have the capacity to give or know how to be gracious. In a way I feel sorry for your Mom because she is a hurt and damaged person she lost out on a wonderful daughter too, how sad is that?! If you take away the "Mother" label she is just another person you know who lives far away......