Drayton Sawyer introduces her to Jason Vorhees as Aunt Amelia and as member of the family, although she's dead, apparently for some time due to the state of decomposition of the body, after falling down the stairs.
We see her in the table for breakfast, along Grandpa,Nubbins, Drayton, Leatherface and Jason. During the night, Jason goes to the attic and sees Grandpa holding Aunt Amelia's hand, flooding him with memories and emotions alien to him. Then Drayton appears and asks Jason to help him get Grandpa and granny downstairs for supper.
During the fight between Jason and Nubbins, Jason cuts Aunt Amelia's head with his katana.