12 year old gender confusion

For the few months, my 12 year old daughter has been bringing up that she is confused about her gender. Lately, she has become very outspoken that she is now nonbinary and transgender. For us as parents, this has come totally out of nowhere. She grew up a completely typical girl, even a girly girl. She never had any mention of gender unhappiness or confusion. I wondered where this could be coming from and realized that she has been using her school-issued Chromebook to go on YouTube (I didn't know it was possible to get on these sites on a student device), to view a multitude of transgender teen YouTube accounts and Tiktoks. It just doesn't sit right with me, and I feel that her opinions/personal beliefs have possibly been distorted and shaped by these accounts she has been viewing over the last several months.. I hate to frame it like this but "brainwashing."

So, I talked to her about her being transgender. I said "It's fine if that is who you feel you are but I want you to give it time. We aren't going to be changing pronouns or changing your body. You are still so young and so much can change in your adolescence." According to her and a few family members, I am being "transphobic" by holding this opinion. I don't want to invalidate her feelings but I also am struggling with having a kid suddenly want to change their gender at, to me, a very young age. I should also mention, my daughter is not diagnosed (and probably won't be get one) but I suspect she may be very close to the autism spectrum, which for me, I feel she often feels "different" from other girls.. well, because she is. But, it isn't necessarily because she's not a girl. It's because her brain works differently than her peers sometimes.

I guess I'm just looking for advice on how YOU would approach this if your child was going through this.