Ms. Ayala, 48, died on June 17 of an embolism after the police say Ms. Castillo pumped silicone into her buttocks and thighs. Ms. Ayala had traveled from her home in Philadelphia to Ms. Castillo’s apartment on Seward Avenue for the illegal procedure.

Ms. Castillo could not be reached for comment on Wednesday because she was being held in jail pending an arraignment. Her lawyer, Robert Osuna, said he had not yet read the criminal complaint and could not comment on it. “We’ll have to see what the charges allege,” he said.

Buttock enhancement surgery, known as a “Brazilian butt lift,” has skyrocketed in popularity in recent years, driven in part by the allure of famously curvy pop-culture figures like Beyoncé, Kim Kardashian and Nicki Minaj, plastic surgeons say.

Cardi B, the former exotic dancer turned hip-hop superstar, told GQ Magazine last year that she received silicone injections in her buttocks and thighs for $800 from an underground medical clinic in Queens. The injections, she said, were performed without painkillers and leaked for almost a week.

In New York City, the authorities have seen a surge in illegal clinics catering to women who want to change their shapes but might not be able to afford a licensed plastic surgeon. The procedures can be fatal, as silicone injected directly into tissues in the legs can be carried by veins to the heart and lungs.