Part or perhaps all of the problem is that as long as you still have breasts, your mother can think of you as a female and dismiss the fact that your hair is short and you are wearing male clothes. Having the surgery makes it real. It brings you mother face to face with the fact that you are a male and she has to give up all her allusions of you really being a female.
My parents were very honest with me when i was transitioning. When I had the top surgery, my mother cried. It bothered her. She identified with it, and to her, my breasts were a sign, a visible sign that I was a female. When I had the bottom surgery, my father, who is very analytic and stoic cried. Again, this was something that he could identify with and removed the last of what he saw as making me a female.
It takes parents a while to truly understand. For many, its the first time they have had to confront it. It always blows me away with how many parents never even noticed that their child was slowly beginning to look and dress like the gender they identified with. Even the parents who are understanding and supportive go through a period of mental shock. They have to give up their daughter or son, depending on which way you are going. My parents were behind me from the start, and visibly relieved that they finally knew why I was so miserable and depressed. They still had problems though. At one point, my father told me that they felt like they were in a Bill Cosby show. They went to a therapist who worked with the parents of transgenders and read all they could get their hands on. Basically the dream parents when it came to being a transgender.
Even now, 26 years later, my mother slips up from time to time and says her. I think its as important for the person going through the transition to help the parents understand and support them as they go through their own mental turmoil. They have to get rid of the pictures of their