Bangor police have been working on the case since the girl's death, repeatedly interviewing Nelligan and the girl's father, Shane Smith, according to an affidavit filed in court.
Kimberly Nelligan, 33, of Bangor is accused of rubbing the addictive opioid on her toddler's gums about 15 times over the course of two months before the baby died on October 10, 2018, according to court documents obtained by the Bangor Daily News.
An autopsy by the medical examiner's office found that the 1-year-old had passed away due to acute fentanyl intoxication, which likely came from "secondary exposure", the report said.
The mother also sentenced 20-year-old OH cheerleader Skylar Richardson, who was acquitted of murdering her baby but convicted of burying the girl's corpse last week.
Illegally, the drug is often mixed with heroin to boost the users "euphoric effects", according to the Centers for Disease Control and Prevention.
She allegedly admitted using the drug on her other children as a sleep aid in the past, police allege.
The mother reportedly confessed to using heroin once a week in the months leading up to Jordy's death and the child's father told police he had seen Nelligan rub it on their daughter's gums.
Smith said he didn't object to what Nelligan was doing as she assured him it was safe.
"Shane said Kimberly did this to Jordynn for about two months before she died". Nelligan's other two children are aged three and seven.
Nelligan was arrested by detectives Tuesday morning. She's pictured (right) making a rude gesture in court. She is due back in court November 12.
Nelligan was allowed bail on Wednesday under the condition she have no unsupervised contact with minors, no contact with Smith and stay away from drugs, except marijuana.