JACKSONVILLE, Fla. -- A woman accused of having sex with her boyfriend as her 21-month-old son drowned in a bathtub has been sentenced to five years in prison.

Lonna Lauramore Barton, 26, was sentenced Friday after she pleaded guilty to child neglect and lying to police.

Lonzie Barton was reported missing last summer and after months of fruitless searching, Barton's ex-boyfriend 32-year-old William Ruben Ebron Jr., led investigators to her remains in January. He pleaded guilty to aggravated manslaughter and is expected to be sentenced to 20 years in prison.

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His admission came days after Lonna Barton pleaded guilty and agreed to testify against him. Ebron's parents attended the sentencing hearing Friday and his father criticized the decision to give Barton less time than Ebron, reports CBS affiliate WJAX.

"I'm never gonna dispute my son had some involvement but he wasn't alone," said William Ebron, Sr. "True justice for this baby would be equal amount."

Lonzie's remains were too badly decomposed to determine a cause of death. Ebron said the child drowned after being left alone in a bathtub while he and Lonna Barton had sex.

Barton is not a candidate for probation because of unrelated drug charges in Baker County.