Responses
He could always control her memories, what he couldn't do was control her perception at the specific time she noticed him. After finding out about her, he could create a human face which she could also see, he just chose not to for fun. He wanted her to accept him for who he is. In other words, what was impressive to him was her momentary perception, which was pretty impressive even if it wasn't permanent. It was still something out of the norm for him and got him interested. Then, after messing with her for a while, showing his different forms purposely and altering the world, he got attached and yeah. Fucked her life some more.
I wonder why his mind control/memory manipulation works on her now? It seemed like it didn't before and that's why he was interested in her. If he can mind control her now, won't he find her boring and lose interest? Maybe it works now because she actually died and he made this fake version of her or revived her with his power...?