ORLANDO, Fla. (CBS Local) — A Florida mother stabbed her 11-year-old daughter to death to keep the girl from having sex with men, according to an arrest affidavit. Authorities said Rosa Alcides Rivera, 28, stabbed her daughter, Aleyda, at least 15 times in a car on Sunday, then drove her around before going to Winnie Palmer Hospital in Orlando. By the time they arrived at the hospital, the child was dead, according to the affidavit obtained by CBS affiliate WKMG-TV.

Officials say Rivera had accused her mother’s boyfriend of having sex with her daughter. Witnesses told officers that the girl had denied having sex with him, the affidavit said.

She also said she believed her daughter was having sex with men because she “smiled different,” according to the affidavit.

Orange County Sheriff John Mina said there appears to be no validity to Rivera’s claim that her daughter was sexually active.

“We don’t believe it’s credible,” Mina said.

Rivera reportedly first told detectives that a man had stabbed her daughter before running away. She allegedly later admitted killing the child, saying “my baby is gone,” according to the affidavit.

She also allegedly told authorities she tried to make the girl more “comfortable” as she stabbed her.

An off-duty Orlando police officer who was working security at the hospital at the time arrested Rivera.

Rivera had cuts near her wrist and was taken to a hospital, where she was cleared medically, officials said. Investigators believe her injuries were self-inflicted.

Rivera faces a first-degree murder charge. She’s being held without bail in the Orange County Jail.