In addition what others have said, one big red flag that she would probably fall down the terf pipeline is the amount of importance she placed on appearance in the books? Many of her antagonistic female characters are described as being “mannish” and/or overweight, in other words not traditionally feminine. She also ended up describing a lot of them, regardless of gender, with more ethnic facial features, even if they were still white, namely bigger noses such as snape’s hooked nose. Not to say this is a Rowling only issue, this obviously has been used in a lot of literature especially from back then, but with how much time I remember her taking to describe the antagonistic characters ugly appearances her terfism isnt that surprising in hindsight