she has said lots of times she wishes she were a boy and seems sad to be a girl
This does not necessarily make her trans. I felt and said similar things when I was a girl.
I never had gender dysphoria or any distress over having a female body.
But I did have certain interests and enjoy certain activities that were considered more suitable for boys, plus a disinterest in some more stereotypically girly things, so there was a definite element of "if I was a boy then it would be okay for me to like this" and "I'm sick of people acting like I should want to do (girly thing), if I was a boy I wouldn't be expected to do this". And then later on, when I started to become aware of how differently society treats men and women, there was an element of "I wish I was a boy because men have it easier than women"
So for me, none of my saying I wanted to be a boy or being sad about being a girl was about me actually wanting a male body, it was about my discomfort with the roles society tries to push onto girls and women, and my frustration about the inequalities that still exist in our society between men and women.
Clearly you know your DD better than anyone here, but is it possible that some of this might apply in your case? That maybe it's about other people making her think she shouldn't be doing "boy" things when she's a girl, when not about a deep seated distress about having a female body?
(Not accusing you of telling her she shouldn't do xyz because she's a girl BTW. IME I got far more messages about what girls should do and be xyz from wider society than I ever did from my parents.)