A Missouri mother authorities said allowed her boyfriend to sexually assault her infant daughter, who later died, was sentenced to 25 years in prison.

Jessica Lynn Howell, 26, was sentenced Friday during a St. Charles County court appearance after she admitted to encouraging her boyfriend, a registered sex offender, to sexually assault her 4-month-old daughter in December 2012, the St. Louis Post-Dispatch reported.

Baby Ashlynn Lillith Peters suffered multiple serious injuries, including blunt force trauma to the head, bruises to the chest and abdomen and internal bleeding related to the sexual assault, according to court documents obtained by the newspaper.

"This mother tragically failed to protect her child in the most disgusting, unthinkable, and unnatural way," St. Charles County Prosecutor Tim Lohmar said after the sentencing.

Howell, who has two other children, was pregnant when she met Jordan Lafayette Prince on Facebook, police told the Post-Dispatch.

Prince, 26, is a sex offender who police said sexually abused a 4-year-old child in Idaho - information Howell learned about through online research. But she continued the relationship, speaking to Prince about the abuse and sending him texts encouraging him to perform sex acts on her then 1-month-old daughter, court records say.

Howell, from O'Fallon, visited Prince's St. Charles mobile home with her baby to spend the night.

On Dec. 2, 2012, paramedics arrived and found Ashlynn not breathing. She was transported to a hospital where she died the next day, the newspaper reported.

An autopsy concluded the baby died from asphyxiation, apparently brought on by strangulation during attempts to stop her from crying. She had a wound on the left side of her head and bruises on her arm, back and legs.

Even if she weren't strangled, the child still would have died due to the internal bleeding, court records said according to the newspaper.

"Don't you have any remorse?" Circuit Judge Dan Pelikan asked Howell after she pleaded guilty to felony abuse of a child and felony murder. "Don't you wish you had your baby back in your arms?"

Howell began crying and said, "My actions were foolish. I didn't understand the weight of my actions."

Officials said one of Howell's two remaining children is in foster care and the other has been adopted, the Post-Dispatch reported.

Prince was arrested and is to be tried in March on charges of child abuse, forcible sodomy and murder.