Riverside County prosecutors filed felony sexual assault charges Monday against a former teacher and administrator who was investigated after one of her accusers went public in a YouTube video.

Andrea Michelle Cardosa, 40, faces 16 counts involving aggravated sexual assault and lewd acts on a child under the age of 14, the Riverside County district attorney's office said. Cardosa was arrested on a $5-million warrant Monday evening in Perris, officials said, and was expected to be arraigned Thursday.

Prosecutors said two victims had been identified. Jamie Carillo, 28, said Cardosa began sexually abusing her in the late 1990s, when she was an eighth-grader at a Riverside middle school. An attorney for the other woman, identified only as "Brianna," said his client was abused in 2009 and 2010, when she was a 14-year-old middle school student in Perris.

Carillo secretly recorded a phone conversation with Cardosa and posted the recording on YouTube on Jan. 17. The video was viewed more than 1 million times in a week but has since been taken down.

In the nine-minute recording, Carillo is shown dialing a number using speaker-phone mode. A woman answers, telling her she has reached Alhambra High School. Carillo asks for "Andrea Cardosa" and is redirected twice. Then a woman answers and agrees that she is Cardosa, a vice principal at the high school.

"You brainwashed me and you manipulated me.... What you did was wrong," Carillo says in the video.

"It wasn't anything I intended," the woman says quietly. "I don't even know what happened."

"You ruined my life. You ruined my childhood. Do you realize that?" Carillo responds, her voice raised. "You sicken me. You sicken me. And every day when I think about what you did, you sicken me."

"I regret it every day," the woman says. "Every day."

Alhambra Unified School District Supt. Laura Tellez-Gagliano said school staff received an email with a link to the video the day it was posted, and immediately reported it to police. Cardosa resigned a few hours later.

Within days, the second woman came forward, prosecutors said.

Luis Carrillo, who is representing the now 18-year-old woman called Brianna, said Cardosa manipulated his client and her mother, telling them she wanted to be the girl's "mentor and friend." Carrillo said Cardosa took Brianna on overnight trips and gave the girl gifts such as movie tickets, food and candy bars.

Carrillo said his client, who has filed civil claims against the Riverside and Val Verde school districts over the alleged abuse, was "happy" that criminal charges had been filed.

"This begins the process of justice in the criminal case," he said.

Though there were initial questions over whether the recorded conversation could be used as evidence — California law generally prohibits individuals from recording people without their knowledge — Carillo's attorney, David Ring, said he believed it would be admissible in court.

"Jamie is very grateful Cardosa has been charged with some very serious crimes," Ring said. "She hopes justice prevails."

Before arriving at Alhambra, Cardosa worked for three other school districts, teaching, serving as vice principal and coaching girls' sports. Officials at those districts said she passed all necessary background checks each time she was hired.

kate.mather@latimes.com

frank.shyong@latimes.com

Times staff writer Richard Winton contributed to this report.