Okay, I was thinking about this. Melissa should be an animorph and it really makes sense. Think about it, Chapman keeps showing up in the story, he's a main character in TAC. David got to be an animorph because his parents were controllers and because he had no where else to go. He didn't even want to fight the Yeerks. Melissa would have, as seen in MM3. Also, if the animorphs had memories of that alternate timeline and knew that Melissa was an animorph and good at it, why didn't they bring her on afterwords? It just doesn't make sense.