How come HIC had both Vriska's and Tavros's mind power?

http://www.mspaintadventures.com/?s=6&p=006758

GT: Cripes the things she told me now that i think about it. She said the witch even killed her dog!
GT: Is that true?
TT: I don’t know, but wouldn’t doubt it.
TT: There are other urban legends that she did a lot of experiments on animals and people. Mostly to do with mind control.
TT: Like figuring out ways to unlock all of her psychic alien potential, to increase her power.
TT: Not sure if that’s true, or if it was actually successful though.