I don't believe her.
From https://www.si.com/college/2022/03/03/lia-thomas-penn-swimmer-transgender-woman-daily-cover:
“I just want to show trans kids and younger trans athletes that they’re not alone,” she says at the coffeehouse. “They don’t have to choose between who they are and the sport they love.”
“I don’t know exactly what the future of my swimming will look like after this year, but I would love to continue doing it,” Thomas says. “I want to swim and compete as who I am.”