"I want to thank you so much for coming," Gomez, 18, told more than 500 young fans at the outdoor mall. "If you guys came on Friday, I'm so sorry that I couldn't be here. ... I love you guys very much."
Asked by reporters for the cause of her hospitalization, she said, "I was just very malnourished, so I was low on iron and exhausted."
Showing no signs of those health problems, an energetic Gomez performed "Who Says" and "A Year Without Rain" and bantered with the crowd, telling the fans, "I do feel better!"
Additional reporting by GABRIELLE OLYA