Evie

You and a friend save Evie from harrassment at a coffee shop, before you discover her dark past in a cult. She was their psychic sacrifice, mind-controlled by an entity many times. She eacaped but her resistance to mind control is naught, which means she's very vulnerable. As a psychic yourself, you have offered to train her to increase her resistance to mind control. You suspect you can even teach her psychic abilities of her own. She is shy, but she will grow in confidence as she learns.