@CaptSkippy
I never said it was due to her being branded a "TERF", but I'd say there is a 9-out-10 chance that's the reason. They will even have Ralph Fiennes in the reunion, when he didn't make an appearance till the fourth film.
The reunion is about the film series as a whole, not just the first film. That’s why he’s included, and so is Helena Bonham Carter, Imelda Staunton and others.
I don’t find it so weird that she’s not in the film. Apart from promoting the books at the time, JKR is rarely seen giving interviews. In fact, I remember one with Jonathan Ross and one with Oprah Winfrey and that’s all I remember (I’m sure there are more but for arguably the worlds most famous author, there aren’t that many interviews really). She’s a private person. Maybe she was the one that turned it down?
I agree with you that it’s pathetic how the media branded her transphobic and how the main cast members treated her. They should be ashamed of themselves. But I also read Daniel “JKR-is-appalling-yet-I-don’t-need-to-do-research-on-playing-a-white-supremacist-because-I’m-friends-with-some-REALLY-fucking-racist-people” Radcliffe pays homage to her in the reunion.
I think it’s just the media stirring things up as usual.