Sabrina Siconolfi entered the plea in court on Tuesday.
She was originally facing a manslaughter charge. That charge is now expected to be dropped.
Siconolfi, 32, Toronto, was arrested in July 2010 after paramedics were called to her apartment near Victoria Park Avenue and Lawrence Avenue East on July 9.
Her daughter, Sakina, was not breathing.
The apartment was found to be 31.5 degrees.
A post-mortem report indicated Sakina "died of heat stroke from exposure to a hot environment in the context of multiple inflicted injuries."
Dr. Michael Pollanen said, in his opinion, the injuries, "compromised Sakina's health and made her unable to regulate her body temperature."
Paramedics also noticed other suspicious injuries.
Sakina had 24 bruises on her back and some abrasions. At least six bruises and many abrasions on her upper limbs, and another 10 bruises and abrasions on her lower limbs.
She also had a healing fracture on her right ribs.
Siconolfi had full care and control of Sakina in the days prior to her death. She acknowledged she was responsible for her daughter's well being and failed to take reasonable steps to seek care for her.
She admitted some of the injuries identified in the post-mortem were caused by her.
Siconolfi will be sentenced December 14.