Thanks for helping me work through this, Happyflowergirl. It wasn't that I was forbidden to grieve my mom's death, but it did seem as though there wasn't much time to do so. My dad worked 3000 miles away Monday-Friday, and I had to manage the house, my younger brother, plus school (I had just turned 15). I don't remember grieving much, but it just seemed as though it was inevitable and wasn't something I could control. I do remember, though, that my dad was upset one evening and told me that if I hadn't been such a difficult adolescent, my mom would have been less stressed and able to quit smoking (she died of lung cancer). In retrospect, I'm pretty pissed off at him for saying something like that to his own child, but I don't remember what kind of reaction that I had. I don't think I bought into his guilt trip, though.
Until this summer, I don't remember ever "wishing" that my mom hadn't died. My husband and I went back to my dad's house in July to clean out the attic, and I found a lot of mementos that brought back memories of her, and for the first time in over 20 years, I cried myself to sleep wishing that she was still alive so that I could have known her better.
I was thinking about this all a lot today, and realized that the problem is not my stepmom's behavior. The problem is that my expectations of her are probably not realistic given our situation. I guess there are some things that I just need to learn to accept.
Thanks, all of you, for helping me realize this