Mary Ann "Polly" Nichols (née Walker; 26 August 1845 – 31 August 1888) was one of the Whitechapel murder victims. Her death has been attributed to the notorious unidentified serial killer Jack the Ripper, who is believed to have killed and mutilated at least five women in the Whitechapel area of London from late August to early November 1888.
Jack the Ripper was a woman.
Since we don't know the actual identity of the killer, we can't say for sure that they either are or aren't a woman. I think the system used the description of the case and assumed male.