We can't know for sure, and I won't definitively say it or use male pronouns for her. But a lot of her past comments hint that she may actually be a repping trans guy. Hell, some of the broader themes of Harry Potter are trans-coded. It would explain a lot. This seems very personal to her.
And at this point, if she really is a repping trans guy, could she even come out and transition? If she did, it would be a very lonely experience. It's not like she would be welcome in the trans community. You can't do that much harm to a group, even while secretly a member of that group, and expect to be accepted by them. And she would in turn lose all her connections among the TERF crowd.