I guess it depends, I've been a staunch supporter but even I think she's now veering into the right-wing 'trans Women are Men'! Way of thinking.
For me, with this tweet it's
1. The timing, being Pride month is like shouting down the BLM movement during black history month.
2. The need to mock the definition of Woman, now that it has expanded she's having a definitive dig at the trans community, I'd think if I was a trans Man I'd find it more offensive, she's basically invalidating them, saying they're still just Women who menstrate, whereas, they're trans Men who are undergoing an extremely difficult journey. The last thing they need is for Rowling to be pointing these things out.
As for me and many other trans Women, we know we can't menstrate, we don't need to be told. It's like telling a blind man he can't see and real men have 20/20 vision.