I'm going to preface this by saying it will probably be extremely long, just because there's nobody in my life I've been able to tell this story to before. People talk shit about Kiwi Farms but you guys are honestly the most open to different opinions than anywhere else online, at least in my experience. Hopefully I won't get kicked off the thread for this but I am a transgender man/FtM (diagnosed with gender dysphoria by a therapist), this is important for context.
In my senior year of high school, I met the person who I ended up having my first serious relationship with, I'll call them J. Some more background information for context: J is biologically male and a legitimate diagnosed autistic (but high functioning enough to pass as "just weird"), they probably have some other mental health problems that are undiagnosed. We're the same age, went to different high schools. When this story took place we both identified as pansexual and polyamorous.
We met online and hung out for the first time at a local park. J was funny, easy to talk to, very accepting of me, and I thought they were cute. We chatted a lot (online/over text and in person), never had any red flags except for J making more sexual jokes than the average person - I just assumed it was from a mix of autism and immaturity.
After a few weeks, we started officially dating. Everything was still pretty normal. J ended up being my date to senior prom. We rented suits from a local shop, they never objected to that or to anything traditionally masculine. That night was the first time we had sex because it's a cliche teenager thing. After that was when things first got uncomfortable. J was always making sexual jokes and trying to initiate sex - again I assumed it was autism, plus just being a horny teenage boy. I did eventually say it made me uncomfortable and J said they would try to stop, but they never did.
A few months passed, we both had graduated and were spending more time together. Two things happened pretty close together. The first was that J started (online) dating this girl, who I later found out was trans MtF. I liked her decently well, but she was very shy/needy/anxious/etc to the point where it felt like she was a literal anime trope, and she would constantly make overly sexual flirtatious jokes with J. Even when I was hanging out with J in person, they'd be messaging her.
Also around this time, but a bit later, J told me they thought they might be a trans woman. I was supportive but pretty surprised - throughout our relationship I had no reason to think J had any gender dysphoria (because they didn't). In our group chat together, J and their girlfriend would constantly be talking about their "girl cocks" and just saying very sexual things. I would just leave the conversation when this happened because there was no convincing J or their girlfriend that "girl cocks" are not a normal topic for casual discussion.
I was as supportive as I could be. I agreed to use she/her pronouns and call J my girlfriend. I did their makeup. I helped them choose a new name. I offered to look for feminine clothing with them at the thrift store or teach them to shave their legs, but they declined. They hadn't come out to their parents (and wouldn't for a long time) and they said they weren't dysphoric and the only "girl clothes" they really wanted was underwear. I loved them, but not enough to take them panty shopping.
We broke up after dating for a little over a year (for reasons unrelated to their transition) and agreed to stay friends. I was obviously hurt and didn't want to talk to them very much, especially for the first couple of months.
During our brief conversations (usually with months between them) I learned that:
-J had formed a small hive of online trans girlfriends with some convoluted web of how they were all dating/e-fucking each other
-They had started taking estrogen from a friend's prescription
-Friend was also 5+ years older, may or may not have been sexually involved with J
-J had decided they're a lesbian (despite having been attracted to me at some point, and only being interested in trans women)
-Countless new transbian girlfriends and breakups, I can't keep track
-Accidentally being outed because their mom found the estrogen pills J was illegally taking
-J had apparently realized they were trans because of me; I never knew until they told me that way after and I was a bit horrified.
After all of the drama, talking less and less often, J still making sexual jokes and flirting with me, I cut contact.
It's been a few years since we had talked and J recently reached out to me, wanting to catch up. We talked online for a little while. They're single and living a few states away but may be moving back soon. They're stopped taking estrogen (apparently this is temporary) and my general impression is that, although they haven't said it out loud, they regret transitioning or possibly realize they are not actually a trans woman.
I want to be supportive of my friend. They're lonely and depressed. I'm the catalyst for them leaning too hard into a femboy/lesbian/whatever fetish and kind of ruining their life, so I feel like I at least owe them some help. But I honestly don't know what to do or if there's even anything I can do.