LOS ANGELES (AP) — “Harry Potter” author J.K. Rowling is facing hefty backlash after she posted a series of tweets about transgender people.

Rowling drew outrage Saturday on Twitter when she criticized an opinion piece from Devex that used the phrase ”people who menstruate.”

“I’m sure there used to be a word for those people,” the famous British author tweeted. “Someone help me out. Wumben? Wimpund? Woomud?”

She continued with another thread speaking about the concept of biological sex.

“If sex isn’t real, there’s no same-sex attraction,” she tweeted. “If sex isn’t real, the lived reality of women globally is erased. I know and love trans people, but erasing the concept of sex removes the ability of many to meaningfully discuss their lives. It isn’t hate to speak the truth.”

Rowling’s tweets caused a firestorm of responses from the LGBTQ community and others who were upset with her words. A Harry Potter fan group tweeted its disapproval of Rowling’s post and encouraged followers to donate to a group that supports back transgender women.

Rowling said she respects “every trans person’s rights to live any way that feels authentic and comfortable to them.” She went on to say she would march “if you were discriminated against on the basis of being trans. At the same time, my life has been shaped by being female. I do not believe it’s hateful to say so.”

GLAAD issued a response on Twitter, calling Rowling’s tweets “inaccurate and cruel.” The advocacy organization dedicated to LGBTQ equality then asked those upset by the author’s comments to support organizations that help black transgender people.

“JK Rowling continues to align herself with an ideology which willfully distorts facts about gender identity and people who are trans,” GLAAD tweeted. “In 2020, there is no excuse for targeting trans people.”

Rowling’s representative has not responded to an email request for comment.