I feel emotionally involved in this Slowlygoinginsane24, because as I said before, I can really relate to what your daughter is going through - though she has experienced more difficulties in her 12 years that I did in my childhood, so I acknowledge that she has more things going on than I had.
I mentioned that I considered taking my own life rather than growing up female - I found out where a neighbour kept his shotgun - and that was in between finding out about periods, and my periods starting.
It sounded absolutely horrific to me, and was the 'last straw' as far as being a girl was concerned.
But when my periods started, I just went 'Oh well...' and got on with it. Looking back on it, it was astonishing how my attitude change - and it's very revealing about how dramatic young teenagers can be, but also how pragmatic when push comes to shove.
I think 12 year olds have to know about periods, but the info can be presented in a very matter-of-fact way, de-escalating way - 'it's just something that happens, girls deal with it, boys are lucky they don't have to, but hey, millions of girls and women manage it and it doesn't stop them doing whatever they want in life'.
I think what I'm saying Slowlygoinginsane24 is that you communicate not just through words but through attitude, and if you can manage [I know it's very very difficult for you] to communicate strength, confidence, experience, steadiness, along with the great love you clearly have for your daughter, she'll pick up on the fact that you were a girl, you are a woman, and you manage OK.
One of the unfortunate things about the trans movement is that it tries to keep gender-questioning people in a constant state of worry, up to and including that trans people are 'marginalised' or even 'genocided'.
Gender-questioning children like your daughter may be picking up on that artificial trans panic, so trying to be calm and clear and strong about the fact that she is a girl and the fact that she is a woman - but whatever kind of woman she chooses to be - to counteract that.
It's a huge ask of you, I know, when you too are under so much pressure, to try to act strong and calm when you're probably feeling anything but!
Your daughter is lucky to have a mother who is going to great lengths to work out what is the best approach to take with the little girl she loves, to help her grow up to be a strong and happy woman.