The link above to Helenas story 'by any other name' details her own personal experience of this phenomenon and how it encouraged her to transition.
Did you read it?
As someone who did read it, I can testify that a lot of Helena's online experiences were very familiar to me (I'm similar age to her, ex-Tumblr lurker, ex-fangirl). Although I wasn't a huge Tumblr user at that age, I was on another, more niche forum website that had similar dynamics, although it was nowhere near as bad as Tumblr.
Like Helena, I was obsessed with boys. Mostly fictional boys -- cute, respectful anime boys in anime and fiction either aimed at or written by teenage girls. I didn't like real teenage boys much because so many were obsessed with sex, and they were usually a bit spotty and smelled like Lynx on top of days-old BO. But the ones in the stories were sweet and handsome and if it was a gay love story, that was even better, because I didn't have to confront how a woman might be expected to fit into this relationship (and the female characters were usually so boring I got annoyed at seeing "my" male character so obsessed with them).
For a while, I wanted to be a gay anime boy. I didn't cut my hair, mostly because my preferred fictional crushes had long swishy ponytails, and I switched to wearing less feminine clothes. It was more a fantasy desire than an identity, but the forum I was on was full of teenage girls declaring new pronouns for themselves and I wanted in on this social group. And why not go for nonbinary? After all, that's not female, and I didn't want to have a relationship as a female.
So I decided to tell my dad I was nonbinary, but he thought I was coming out to him as bisexual. For the record, he was completely OK with that. Too embarrassed to push any further, I dropped the idea and went back to being a girl.
Reading Helena's story, my experiences could have been a lot worse. It's chilling to think I was more or less at her starting point, but retreated from it.
I hope she's doing OK now.