I would like to offer Barracus as the role of She-Ra's mentor.
Barracus' mother was mentally and physically abusive throughout his childhood, she was a weak and pitiful thing but extremely skilled in the arts of manipulation. She had Barracus wrapped around her paw and kept him so at war with himself that it didn't occur to him to kill her until he uncovered one of her many lies, that his father
was not dead, and took his revenge. Barracus is slightly insane, he feels as though his mother's spirit watches him still through the eyes of others and has a hand in all the negative things that happen to him. Before his father was killed in the final battle with his mother, he told Barracus briefly about his plans to gather an army of purewalkers and use them to terrorize the Kawani lands and drive them into an age of darkness where evil will reign. When Barracus' father died, Barracus took up his father's cause and traveled to the Kawani lands to work at tearing them apart from the inside. Although Barracus despises the other races for their weakness he is willing to make use of them as pawns to further his own cause and I could see him stealing a basket in order to brainwash it the same way his mother brainwashed him. He would have found a 'nanny' for her and kept them in a safe and secluded area for her teaching, allowing only trusted allied to have contact with her to further her evil education. He would want her out of the way as she grew since he would have no use for a weak child, only visiting occasionally to cement her loyalty to him. He would be kind throughout her childhood but begin to be both kind and viscously abusive in alternating spurts once she reached adulthood, depending on if her progress pleased him(he's a purewalker, can't help the violence and he hates females on principle xD), and perhaps that is what eventually drives her away from him?