Lisa Vanhoff (Janet Waldo; 1920-2016) is a redeemed villainess from "Vampire Bats and Scaredy Cats," episode 2.02 of The Scooby Doo Show (airdate September 17, 1977).
In the episode, Lisa was set to inherit and run a hotel on Skull Island, which was originally run by her Uncle Leon. In actuality, Leon was plotting to have Lisa put away so he could retain control of the hotel, with the plan including disguising himself as a vampire and claiming that it is the ghost of Lisa's grandfather planning to turn Lisa into a vampire.
Shaggy, Scooby-Doo, and Scooby-Dum barricaded themselves with Lisa, guarding her from the vampire. Lisa later heard the phone ringing and answered it, only hearing ringing bells. After hanging up, Lisa turned heel and became a vampiress--flashing fangs and demonic green eyes.
Under her heel persona, the evil Lisa snarled and hissed at Scooby-Dum before chasing the trio out of the room. She was later seen getting into a coffin under the direction of the vampire, but she is revived and freed from the control when Velma wakes her.