Kelli Stapleton, 45, has been released from a hospital where she received medical treatment after police said they found her and daughter, Isabelle Stapleton, inside the family van with two lit charcoal grills in the back seat, UpNorthLive.com reported Thursday.
Isabelle remains hospitalized and unconscious in Grand Rapids. Doctors said she is expected to live, but she may have permanent brain damage.
Michigan State Police Lt. Kip Belcher said there was no indication the teenager had been restrained inside the vehicle.
The van was found in a wooded area in Benzie County where the family lives.
Police said they began a search for the vehicle after Kelli Stapleton's husband, Matt, reported he received a "disconcerting" phone call from his wife.
The mother has written of Isabelle's acute autism and violent episodes on her blog, "The Status Woe," Mlive.com reported.
The daughter ended an eight-month treatment program in August and was preparing to enter a special education program at a local school.
Public reaction to Kelli Stapleton's alleged murder-suicide attempt has drawn both sympathy and criticism.
A Facebook page set up in support of the family says, "Sometimes we are given more than we can handle. Walk a mile in our shoes and save your judgment."
However, Paula Durbin, an activist for the autistically disabled, said she is tired of people citing their personal challenges as a rationale for threatening the lives of the disabled.