You

"Why are you always so mean to Casey?" Vera sniffled. 

"Because he makes everybody's lives more difficult," Kane said in exasperation. "You might be ridiculously nice to people who cause you nothing but trouble but that doesn't mean I have to be."

"He went through something horrible! Just because you can handle something doesn't mean everyone else can handle it the same way. Honestly, his reaction to all of this is more normal than yours. You dismiss trauma way too easily."

"Why are you defending him when all he ever does is upset you? You're sad when he's here and sad when he isn't. If he makes you so sad, why are you even still here?"

Kane immediately looked like he regretted saying that. As if he thought that would be enough to accidentally convince her to leave.