I would support her but at the same time be careful. I have ASD and I too came out as a trans at about the same age. My parents started counselling with A Trans counsellor. But over the years I came to realise that that wasnt what I wanted . I didnt want to be a man, I just didn't feel comfortable in dresses, with boobs etc, it was my ASD confusing me, I dressed like a boy and did boys activities, people expected me to be more feminine and I rebelled. I didn't unserstand that it was ok to wear what I wanted because others often critisied or auggeates I was wanting to be a boy. I found puberty horrible and still do and I was attracted to both male and female. My doctor helped in some way by stopping my periods at the time, it made me feel more comfortable in myself. But by that time people were aware of the fact I had became "Trans", my parents had assumed I was after watching a trans program, I didnt underatand it at all really, just that I was different, so I eventually agreed that I was trans. I began meetings and discussions with doctors etc and started to call myself "him and he", I uses a male name for a few years, and it never felt right, but by then I felt unable then to say "No this isnt what I want" after all. I assumed I must be trans because others didn't think I fitted in any other box.
After the doctor stopped my periods I felt more at ease and happier with my body, but couldnt explain to others, I was approaching time for treatment to change over and it terrified me. I rebelled and self harmed, I ended up in trouble with the law. Then ended up in prison for petty offenses. For most people it would have been horrific but for me it allowed thing to stop and slow down, all interederance and talking about trans stopped in prison. I felt more free and able to be myself, Eventually I worked up the courage to tell my family, but its never been put behind me I often return to my home town and feel so embarressed because people question why I never had that sex change or they ask me if I was the He/She. I was judged by kids at school when I came out and bullied. Then bullied again when I returnes home after prison wanting to be a woman again.
20+ years later I'm now married with a son in a different are, It terrifies me to think how close I came to not been in this position. A friend in one of the trans groups i joined did go through with some changes and now regrets them. Again She has ASD and now cant get rid of facial hair due to the hormones she was given and has to shave twice a day. She has to declare she went from female to male to female again everytime she fills in a passport application or something similar and she now suffers horrific depreasion and suicidal thoughts. I therefore think those on the spectrum need a lot more support with issues like this than they are getting and a lot more time to consider it before taking steps. I allow my son to wear what he wants male or female, but I dont suggest anything to him. ASD can make us open to such suggestions I honestly thought that because someone had noticed I looked like a boy and I was unconfortable with certain thing that I must be trans. Give her all the support you can but dont just assume or let her make rash decisions. If I had gone through with any of it I believe now I'd have commited suicide. I instead became more aware of my ASD and why I felt different. Boobs felt strange, periods were horrible, and I couldnt wear skirts or dresses due to sensory issues, I loved football, gymnastics and climbing trees and computer games and yeah I like women, they may be stereotypically boys things but girls are allowed to behave like that and if people were more open about people been comfortable in their owm body rather than fitting in atereotypical boxes then I'd have felt happier just saying "No I just dont like dresses, periods etc and I'm bisexual"
I always had my hair ahort because I couldnt abide it been on my face not becauae it was a boya cut, it just irritated me. Now I have it long, because I managed to grow it long enough to tie it right back out the way. I have boobs but still hate them and wear baggy tops ans trousers and I still take medication to stop my periods with the occassional break to clear my system.
If your daughter is hanging round with a trans person she may well be thinking that this is the Norm, if you have askes hee if ahe ia trans, she will question it herself, my mum did it out of love, but now I believe it was the worst thing she could have done because if I was truely trans I'd have worked up the courage when I was ready to, to say it, suggesting it to me made me question myself. It makes me more concious of not making that mistake with my own kids. My mum would have been happy signing for me to have the op or start treatement because she believed it was what I wanted she isnt a bad mum she juat wantes the beat ans xouks aee mw unhappy. My dad however didnt think i was reasy to make the decision and wanted me to hold off until I was an adult and just live as i wanted too first, he always made it clear he'd accept what I wanted but he helped me pace myself and take time to stop and think. Thats what I have to be thankful for. Because otherwise I'd have started treatment at first suggestions of mw bwen trans instead I was given freedom to be myself, my biggest regret though was telling others around me that I waa a trans person, school friends, peers etc before I really knew what I wanted myself. Even now I avoid get together with old friends or neighbours becauae of gossiping. You cant take back such decisions, even if the op is reversible eveeything else isn't. Let your daughter live how she wants, give hwe counselling but dont amke the mistake of helpibg her get treatment too soon. Make sure you get her counselling and make aure whoever she ia been aypported by doesn't just specialise in trans issues but also ASD. If Id been able to ait down and diacuaa what was my ASD and what waa sexuality and trans stuff I probably wouldn't have gone as far as I did. The ability to mother a child cant be replaced and thats one thing I am grateful for, that I managed to stop it bedore I loat the baility to become a mum. I know theres adoption etc but its not the same in my eyes. If I'd started treatment I honeatky believe now Id have been sectioned or dead by now. Sorry to spout so long and be so confusing but this is an sisue i feel very perosnal on. Im not syaing your daughter isnt trans by any way. Just that you beed to aupport her propelry though this and dont make rash decisions or suggest how she may feel. Aome peooke with ASD dont know how they feel themselves so having feelings suggested to them is an easier way of dealing with what they dont understand. Make it clear you will live her whatever, but make aure ahe gwta prowpr support and help from both Trans and ASD sides.