Anger motivated her. In the end, she did become fitter, she said, and mentally stronger.

“I was able to prove them wrong, do what they asked, and become a better player,” Horan said.

This spring, Adidas made an ad with Horan that tackled the issue of body image. “Fewer stereotypes, more goals,” Horan wrote on Twitter when she posted the video.

It surprised her mother, because Horan had not talked about it publicly before.

“She said she was ready to share it,” Linda Horan said. “I said that’s great. That’s going to empower so many people.”

“She’s really a good role model for little girls,” Mark Horan said. “And I love that.”

Once she returned to the United States, Horan earned a spot on the 2016 United States Olympic team (starting once for a team upset by Sweden in the quarterfinals) and instantly became a top player in the N.W.S.L. She was one of 15 finalists last year for the inaugural women’s Ballon d’Or, awarded to the world’s best player.

A quadriceps injury this spring slowed Horan, and she played sparingly in recent matches leading into the World Cup. But she scored the third goal in the Americans’ 13-0 thumping of Thailand on Tuesday — a moment that prompted her father, cheering in the stands, to shout, “Our little girl scored!”— and she said she feels 100 percent. That should frighten American opponents even more than Tuesday’s score line.

“This was my route, purely for me,” Horan said. “There’s girls that are the same age as me and went to college and ended up here. It worked out for them. I think that’s great. You find your path and do whatever’s best for you.”