Transnamechange I find it interesting you mention your sister was highly involved with the gaming culture and feel the internet has played a role in your sisters case.
Time and time again this seems to pop up, or people who work within the computing world somehow.
Its almost as if somehow in this is an inability to separate the fantasy world and the world of reality and this conflict and gap between the two is the thing that has created the issue.
For several years I was involved in a gaming community. I deliberately used a male or neutral id in order to not receive abuse and to have an equal status within game and to avoid harassment. The treatment of women within these communities is outrageous. Over time I became more confident in eventually revealing the truth, but only after I have first built up respect. The world contained many young teenage boys on absolute power trips who treated 30 year old women who had kids with utter contempt. Because I built up respect first it put me in a position where I was able, with the support of others, slap down a few for their appalling attitude.
There are also a lot of obsessive personalities that you seem to come across who take whatever they do or say to the extreme and with great seriousness.
My point is, that its a world which is even more tilted towards toxic masculinity than reality. If you emerse yourself in it, as a woman, then you are exposed to that.
There is a twisted sense of the definition of what success is. It seems to value winning over anything else and regardless of how it might impact others personally. It also elevated individuals who were social drop outs into someone who was important.
I find it so easy to understand how girls will see transitioning as the solution in this environment.
I was slightly older than a lot of gamers. Not the only one, but tending to push the limit. I can't imagine how damaging it would be to some of the younger girls involved.