On the eve of her trial for attempted murder, Kelli Stapleton – the Michigan mom and former blogger on autism issues who stood accused of trying to kill
her autistic teen daughter – pleaded guilty Tuesday to a felony charge of first-degree child abuse.
The plea still carries a possibility of life behind bars for the 46-year-old woman. Her sentencing will be determined at a later date.
"This was an extremely serious incident which could have resulted in the death of an innocent child," Benzie County prosecutor Sara Swanson said in a statement shared with PEOPLE. "A conviction of this felony carrying a maximum sentence of life in prison, and the prison sentence we expect it to carry, is the right resolution for the community, the defendant, and our victim, Isabelle."
Isabelle Stapleton – "Issy" to family and friends – was 14 on Sept. 3, 2013, when, according to the prosecutor's office, Kelli Stapleton shut herself and her daughter in a closed van with two lighted charcoal grills. She and Issy were found unconscious from carbon monoxide poisoning.
Both mother and daughter recovered, but Issy spent several days in a coma before achieving what her father Matt, 42, a high school principal, described to PEOPLE in July as an "amazing"
In statements made after her recovery (which Stapleton's defense team had unsuccessfully tried to bar from the upcoming trial), Stapleton said that after years of Issy's physical abuse targeting her and other family members, she "thought this would be the best solution ... if Issy and her went to heaven," according to a police officer whose earlier testimony quoted from court documents.
The Elberta, Michigan, family (which includes Issy's brother McEwen, 16, and sister Ainsley, 13) had also just completed a seven-month separation as Issy went through a residential treatment program 200 miles away.
Her parents saw significant progress from that treatment, but Stapleton's final blog post cited "battle fatigue" when a local school then failed to admit Issy, causing the parents to consider sending their daughter away and dividing the family again.
Reluctantly breaking his public silence, Matt Stapleton said he hoped the incident would call attention to the needs of those raising children with autism, now 1 in 68
, according to the U.S. Centers for Disease Control and Prevention
. He told PEOPLE, "Kelli did something unspeakable. I still love her, but I'll never forgive her."
A friend of Kelli's, who asked not to be identified, tells PEOPLE: "I think there's a sense of relief to a degree. I'm looking forward to Kelli having the opportunity to move on past this, and for her family, too. I think that's important."
"They've all been through so much," the friend says. "Kelli needs to have an opportunity to heal from this, and so does everyone else."