Justina is the faithful maid of Susana San Juan. She has known her since she was a baby, and took care of her mother when she was dying of tuberculosis. She stays with Susana even though she is insane and screams at her all the time.
She takes care of the cats, and Susana often thinks that she let the cats into her room, but actually it's ghosts that she feels. Remember that the next time Fluffy comes and hops on your bed late at night.