Rachel... well, Rachel is really strong.
I guess you forgot #48 The Return? Rachel is not impervious to moments of weakness.
Okay, I will admit this. You are right. Cassie was selfish. She found herself acting selfishly when she quit the animorphs. It was wrong of her to just allow, as Rachel said, "the whole [to] drop dead just so long as you, [Cassie], don't end up turning into me (Rachel)."
But it was in her moment of weakness, after ripping out that Hork-bajir's throat out. It was after those countless war battles. It was after all those nightmares which constantly reminded her of the terrible inhumane things she had done. And being the kind-hearted pacifist it drove her crazy. Take into account the type of person she was and realize that moment was inevitable and necessary for her character development. It wouldn't have worked with Jake, Marco, or Rachel. They weren't as resistant to the effects of war like she was.
It was selfish, alright. Her family, her friends. Cassie gave up on it all just so she could feel morally satisfied. And I don't fault her for that decision. Not one bit. There was too much on her plate and she knew she was losing herself. She claimed she didn't need time to recollect, and that her decision was final, but she wasn't aware that her decision-making wasn't complete. There was an ordeal she had to undergo. One that would change her perspective on the war in its entirety.
And then with Karen, Cassie jeopardized the Animorphs secret by allowing Karen to infest her. But by the time that happen she had come to understand Karen. So much that she was able to anticipate her actions, knowing that Karen was not a real threat to her or her friends. Read the book again. Cassie is a very smart girl.
But i have a feeling that even if she didn't come across Karen, she still would have went back to the Animorphs.
