How we cite our quotes:
"Kevin is seven human years old now, and perfectly normal... aside from the fact that he kept the name Kevin, that is." (3.73)
When a soul takes possession of a human body, they tend to pick and choose what parts of the human's personality to take on. Sometimes they even take on the person's name. Wanda has a similar experience with Melanie that this soul did with Kevin. She pretty much acts like Melanie in every way, stopping short at calling herself "Melanie."
"Curt and I had to pretend to be our hosts for several years." (5.34)
The Comforter's statement makes you wonder how much of her behavior is truly hers and how much is simply mimicked from the humans. Hey, we can't be around our friends without picking up their mannerisms, either, so we sympathize.
I wanted to touch [Jared's] face. I wanted it. Melanie did not like this. (29.112)
Their thoughts and feelings are so intertwined, Wanda thinks she's the one who wants Jared even though she has no reason to love him. He's punched her, disparaged her, tried to kill her, etc. (Well, do you even need more reasons?) It's Melanie who wants Jared, not Wanda. She's reclaiming control of her body when Jared is present. And she probably has to fight him for control, too.