According to one Creepypasta, Jane was a neighbor of pre-insane Jeff. After Jeff killed her parents, she swore revenge against him. She donned a black outfit, a white mask with black eyes and lips, and a knife, and she's been hunting Jeff ever since.To my knowlage she recently killed jeff in a abandoned building.
On and Against Sora's TeamEdit
When she once spotted Jeff fighting against Sora, Stitch, Kenny McCormick, Lock, Shock, and Barrel, Jane decided to join the fight. After Jeff retreated, Jane became furious when he escaped, but doesn't join the team, but assists them only when they fight against Jeff.