The 11-month-old girl stood in the tub, playing in shallow water with a 2-year-old girl, both looked after by a teenage mother home alone. The last moments of normal life in the third-floor apartment on Classon Avenue in Bedford-Stuyvesant, Brooklyn, ended that way, with one young mother, a pot of rice on the stove down the hall and two children in shallow water that would not be shallow enough.

“It was an accident,” said the mother, Jovanna Shiriver.

She is just 18 but looked even younger last month in her new surroundings, a visiting room at a jail on Rikers Island, her hair pulled in pigtails. Short and thin and draped in an adult-size gray jumpsuit, she looked less like an inmate than a girl in a schoolhouse play about jail. She said, “I don’t belong here.”

On July 3, Ms. Shiriver was bathing her daughter, 11-month-old Smeily Ordoñez, and her boyfriend’s 2-year-old sister when she stepped away to stir rice for the children. She returned to find Smeily under the water. When she and neighbors could not revive her, they called 911.

The baby was placed on life support and, in the month since, has remained hospitalized on a ventilator. She was transferred last week from Schneider Children’s Hospital in New Hyde Park, on Long Island, to Blythedale Children’s Hospital in Valhalla, in Westchester County, which specializes in medical and physical rehabilitation.