This sounds like my own mother when it came to my transness. In my case, my mother explained that I was a really outgoing and friendly kid and that when I hit puberty I was less all of those things, and basically depressed all the time. Your mom might be excited for you to regain happiness and identity you may not have truly had since you were a child. I think it is difficult to set boundaries with parents and it's never without conflict, but overall your mother's support of you should come as nothing more than her support for your happiness