Lisa was born and raised in the town of Silent Hill, and went to Midwich Elementary School as a child. With nursing being her family's tradition, she began her career at Alchemilla Hospital. However, it was here that Lisa became addicted to PTV, a drug being dealt by the hospital's administrator, Dr. Michael Kaufmann, and Silent Hill's resident cult, the Order.
One of Lisa's duties was to take care of a patient, Alessa Gillespie, who was severely burned in a fire. Alessa's body was covered in burn wounds which would not heal, and were always oozing blood and pus, requiring frequent bandaging. Lisa did not understand what was keeping the girl alive (the Book of Lost Memories reveals Dahlia cast a magical incantation on her daughter), and the ordeal of constantly replacing the bandages took a toll on her sanity. Alessa misinterpreted Lisa's care as actual affection, something she desperately wanted, having never received any from her mother. This might be the reason why Lisa retains her human form and individuality during the events of Silent Hill.
Lisa wanted to leave Alchemilla and quit nursing Alessa because she eventually grew sick of it. However, Kaufmann refused to allow her, and threatened to cut off her supply of PTV, which led to arguing and fighting between the two.