Judge Frank Fregiato handed down the sentence to the 37-year-old woman Wednesday in a Belmont County courtroom.
Carpenter pleaded guilty to charges of one count of complicity to commit rape, two counts of permitting to child abuse, one count of endangering children, and one count of obstructing official business, WTRF reported.
She will be eligible for parole in 20 years and have to register as a Tier 3 sex offender every 90 days for the rest of her life.
Her 32-year-old boyfriend, who was already a registered sex offender prior to the case, was sentenced to two life terms in prison by the same judge in November.
Police said the rapes happened while Carpenter held down her daughter as Kirksey raped the child, WTRF reported.
It's unclear how many times the child was raped or when the sexual abuse against the girl began.
She reported it to a relative that mom's boyfriend had been abusing her for the last two weeks,' Belmont County Prosecutor Dan Dry told WTRF in July.
'Multiple counts of rape committed by the male, and at least one incident of rape where the mom of the child actually physically held the child down to assist this male.'
Judge Fregiato called the case 'a crime against nature.'
'If a 12-year-old girl cannot trust her mother to love and protect her, who in this world can she ever trust? She certainly wouldn't expect her mother to be assisting in the rape,' Fregiato said during Carpenter's sentencing.