This would be a difficult situation for a mother to handle at any time, but in the current context - and in particular in your DD's social network - it's magnified a 100% by people peddling the belief that it is even possible, let alone desirable, for a girl to become a boy.
I'm sure other posters who are wiser and more knowledgeable than me will come on with advice and links to support organisations, and I hope you get all the support you need.
All I can offer is my own story.
When I was a little girl I wanted to be a boy.
I thought of taking my own life at one point. I had no one to talk to about how I felt, I didn't even have the vocabulary to describe how I felt.
Fortunately, that was before the trans juggernaut rolled onto the scene, so it became clear to me that there was no way I could become a boy.
Nobody offered me social transitioning at school. Nobody had heard of puberty blockers. 'Gender Affirming Surgery'? What's that?? I was so lucky not to have all that to contend with, as it would have been very attractive to me at the time.
What saved me was that my parents loving their little tomboy
,
and above all, knowing the truth- that I was a girl, I was going to grow up to be a woman, and that was that. So I got on with being female. I grew up to be a gender-non-conforming lesbian.
My own personal feeling is that loving support has to be based on the fact that no, you can't be a boy, it's just not a possible, and don't believe anybody who claims it is: but you can be any kind of girl you want to be, and grow up to be any kind of woman you want to be.
All good wishes to you and your DD in getting through this difficult time. I see another poster has, as I expected, referred you to a group that hopefully will give you help and advice and support