I think it's interesting that you have this place to go to. Although I think it is a sign of health as well, in my case I have found it helpful to talk more in depth with someone about these kind of things.
Here's why: when I was in my late twenties, a voice started speaking to me. I took the voice to be that of a friend of mine who had died. I went to a psychic and it was all kind of downhill from there.
It has been many years since then, and now I realize that like Jacob said, it's more important to view the alter personality as a "symbol" of something. Yet finding out all of what it symbolizes can be difficult.
It has taken me a lot of work to put together what this dead friend meant to me and to work to understand the meaning of her life in my life. I had to go through so much difficulty and confusion for many years just to get to the place where I would make peace with the part of me that was "creating" her voice. There is a lot of pain in accepting what had come apart inside, but it is worth it to have more of me back in the driver's seat and have the peace of understanding myself better.
I also wanted you to know that I understand some of the pain around dependency. Although I am not actually dependent on my mother, it is definitely is something that comes up in our relationship. Some of it is in the past, but some of it is also in present family dynamics. While I understand your frustration in wanting your independence, I for one have found it helpful to get the entire picture--dependency and covert incest--before taking deliberate action to do anything on my own. The reason for this is that for us who have been in this kind of situation, the very thought of being independent can carry another negative connotation. In my case, it gives my mother one more reason to get turned on by me!!!!!! Yep, that's how it is. As awful as it sounds, I have found it helpful to go very slowly, step by step, so that I know what I am feeling at each point. That way I know more in my bones what it means to grow.
That's my two cents. Take it or leave it and I wish you the best in every case.
Lose the drama; life is a poem.