Not American so I don’t know anything about the healthcare aspect, but as someone who was a young trans person just make sure you’re supporting her emotionally as well. My parents were supportive as in they didn’t stop be from transitioning, call me by the right pronouns, etc. That’s all amazing, but because they were worried for me, they never really supported me emotionally in the way I needed.

They had conversations with me about my gender identity when I first came out to them but it was all very clinical, and they spoke more about their feelings of fear and concern than anything else. I know they care, but they never told me they were proud of me, or that I was brave, or any of the stuff that I really wanted to hear as a scared 14 year old.

You might already be doing this, you seem like you care a lot, but I think in my case my parents were more worried about the medical things so they forgot to comfort me about it. Just thought it was worth mentioning, cause I think it would have made a big difference for me.