A sex worker has tearfully admitted lighting a fire that killed a couple and their baby daughter in a townhouse blaze in Melbourne’s south-west suburbs.

Jenny Hayes on Wednesday pleaded guilty to three charges of arson causing death over the fire at a Point Cook property on December 2, 2020, that killed Abbey Forrest, 19, Inderpal Singh, 28, and their three-week-old daughter, Ivy.

Hayes sobbed as she entered a plea of guilty to each charge while on a video link from prison before the Supreme Court, as family members of the victims watched the online hearing.

Forrest and Singh moved in to the Totem Way townhouse in the weeks before the blaze, around the time of Ivy’s birth.

Neighbours who saw the fire frantically tried to hurl an axe and throw rocks through a jammed upstairs window when they heard screams for help. The young family couldn’t be saved.

Hayes last year pleaded not guilty to three charges of murder and was to stand trial, but pleaded guilty to the lesser charges after negotiations between her lawyers and prosecutors.

Judicial registrar Tim Freeman vacated the trial when the woman pleaded guilty to the lesser charges, which carry a maximum of 25 years in prison.

Arson causing death is a charge similar to manslaughter, where an accused did not intend to cause someone’s death, and applies to a fire being deliberately lit.