actively campaigns for children to receive hormone therapy
I'd be tempted to throw a couple of curve balls from recent times in to the conversation e.g.
"I wonder why that gender clinic nurse from the US who is married to a trans man is now blowing the whistle on children receiving hormones and therapy"... "I wonder why Caitlyn Jenner is now campaigning to stop children getting medicalised gender affirming care".... then I'd step back and see what she says.
It's very Jeremy Vine with his pretend naivety but handled in the right way, in the right tone at the right time it might provoke a different thought process on that front.
As far her own non-binary status, this could be a positive for her. It depends on whether it leads to her deciding to have surgery to match her particular gender identity - that's a whole different ball game.
Being non-binary, followed by identifying as a man is a well trodden pathway for autistic females, many of whom don't understand the accidental conflation of gender incongruence and "classic" autistic female presentation (many are androgynous, many prefer "boys'/men's clothes, many develop a deep interest in certain concepts - for example). However, for some people gender identity seems to be a very positive thing, particularly non-binary identities. A non-binary identity is different from an identity where someone has a belief that they are of the opposite sex. From my basic understanding it seems to be more like "I sometimes identify with a masculine side of myself, I sometimes identify with a feminine side of myself". I don't have a gender identity but if I did, I could empathasise with non-binary on that basis.
It's a problem where it impacts others' boundaries or can lead to a pathway that may not be right for the individual. Add in autism and I'd say that is highly unlikely that it would be the right pathway for anyone if it leads to them wanting to alter their own body. Almost without exception, I'd say that an understanding of autism needs to be front and centre before thinking about gender.
Medicalisation for gender dysphoria will only be the right pathway for a vanishingly small number of people who have it - from early studies 80% of gender dysphoric people will establish a peace with their own body. With the huge numbers of people presenting with gender dysphoria since that statistic was published (in the 80s I think), that number must surely be higher. Unfortunately it's impossible to know as therapeutic practice has changed completely, from watchful waiting to gender affirming, as has the cohort, from mostly young boys to distinct groups (autistic adolescent girls, gay men and men with the 3 letter acronym issue to name a few significant groups).
I do think it's a valid question from a PP. What do you want her to do? Are you worried about her leading herself or others towards harm? If so, what next? Personally I'd start with something like the questions I threw in earlier as it does seem like she's currently a part of what is leading many children down a lifelong medication pathway that is unlikely to be right for them.