Gimme Shelter tag
Amara wants to trust Dean but she knows better, isn't naive. He may have promised not to hurt her but he didn't say anything about anybody else. Chuck needs to be stopped, there's no doubt about that, but Amara isn't ready to die (and desperately hopes Chuck doesn't either, no matter what he's done). Shit is about to go down and she's terrified about what that all entails.
But Amara will act innocent and is willing to listen to the Winchesters' dumb plan to take her brother out. Until the bitter end, she's game to see how this plays out.