Jane was an unseen villainess from "Death In The Family", mission 2 of Hitman 3. The missions's events saw Zachary Carlisle, a wealthy aristocrat poisoned to death in his bedroom after the entire Carlisle assembled to hold a fake funeral for Alexa Carlisle (the mission's assassination target).
The investigation of Agent 47 revealed that it had been Emma Carlisle (Alexa's daughter-in-law) who had been responsible for the killing. A letter found in Emma's room also revealed that her mother Jane had instructed her in her murderous plot. Additionally, the two villainesses also plotted to murder Alexa as well.
As it turned out, in her youth, Jane had been the secret lover of Gregory Carlisle, the older brother of Zachary and Alexa who had impregnated Jane and planned to marry her, despite her lower-class background. However, before he could so, he was killed by his siblings, who wished to inherit the fortune and disguised the death as an accident.
In response, Jane turned heel and began decades-long campaign of vengeance that included Emma marrying her cousin Gregory and integrating herself into the family. After killing both Zachary and Alexa, Jane planned to claim the fortune for herself and live in luxury.
A news report in a later mission indicated that Emma was found out and arrested, although the fate of the evil Jane was left unrevealed