Jessica is the villainess from "A New Woman," episode 3.12 of Monsters.
She was played by Linda Thorson.
In this modified version of A Christmas Carol, Jessica is the greedy and heartless wife of wealthy Thomas, who was at death's door. She is the sole heir to Thomas' fortune and his business, and she had planned to have her husband sign an agreement to tear down a homeless shelter and build a high-rise, which Thomas does.
After coercion from Thomas' nephew, David, convinces him to change his will, the evil Jessica planned to pull the plug and kill Thomas, but she was caught in the nick of time by The Doctor, who warns Jessica to change her evil ways or by visited by horrific spirits. Jessica scoffs at this, but she is placed in an alternate reality where Thomas passes on and she inherits his wealth. In that reality, however, Thomas returns as a ghoulish spirit and haunts Jessica, who underwent a ghoulish transformation of her own. Realizing that this is the fate that awaits her, Jessica tore up the agreement and set up an account for David.
Jessica, back to normal, wakes up and sees that Thomas miraculously recovered. She began lamenting about losing out on some of her finances, but when she sees her ghoulish hands, Jessica recants and celebrates Christmas with Thomas and David.