Just wondering, were you allowed to grieve the loss of your mother? In some cases like this, the child takes over for the mother and the other parent thinks things are okay because the child is so strong. I could be way off. But you know what, it is okay to grieve for you mom now.
I am sure your stepmom is bringing back hurt that you felt when your mom died. It makes sense really. But is sounds like you enjoy her even after all these years. Maybe you two can work out a good relationship between the both of you that both of you are happy with. I hope you are okay. (((((LMo)))))))
My dad died in 1999, and I am finding I am grieving some now for the first time in years. I am 39, and sometimes you just want your parent, my dad in my case. Take care of yourself.