Sure, I don't mind. For me, I specifically remember one moment: I was sitting with my mum in a doctor's waiting room and saw a woman get up and leave (she was walking downstairs, and her cleavage just bounced - sorry, there is no other term to say it). And I remember thinking to myself at that moment: No, oh God no, please no, not me. Was about 8-9 years old. But being quite sheltered I had no idea about biology (I thought babies were born through the navel for instance), so I thought as a female one could simply refuse to get that body part (I did not even know the term for it). And that I would refuse for sure, and I wondered why women would even choose to look like this. Because if I had a chest like that, I would be bouncing downstairs like that woman one day, I wouldn't be able to run around anymore, and for some reason I also thought it would hinder me climbing trees (?!).
Also - and in hindsight I think this was crucial - my mother had a cup C-cleavage after having several kids (she lost one, too), and I saw her being physically abused more than once. So I guess I merged these two things in my head without being aware of it: having cleavage, being a mum, procreating, and being abused, being stressed all the time, cooking and cleaning, crying to no end, and no fun ever. Naturally I didn't want to sign up for that.
Later, as a teen in my school, I just noticed that all of the boys and all of the male teachers (yeah) seemed to have one type, and one type only: frail, ballett dancer-looking girls, not too tall, somewhat androgynous, looking like they could break, frankly looking childlike. (I'm from continental Europe.) So that was the pipeline into Americas Next Topmodel, which was the pipeline into anorexia and worse grades, which was the pipeline into thinking I don't want to be a girl at all. Because being "trans" would be the lighthouse in an ocean of doom options, it would allow me to cut my hair and wear loose shirts and sneakers most days, and there would simply be no other way on earth to be able to do those things without being called a lesbian, which I'm not. It would allow me to escape from people's pornsickness as well.
Not saying it's anything like this for your daughter, though, especially since she's so very young. Everyone's got their own way of thinking. Just give her as much love as you can, that's the only thing that gets anything done, really. Hopefully she'll also be loved by other people, along the way, and as she grows up, it will make her come to her senses.
(Also try to cut her time spent on social media if you can.) Crossing my fingers for your family.