The Night King was a threat bigger and far more important than anything Cersei could ever hope to do. That battle at that time to them was the most important thing, Night King had to die no matter what, no matter who died. Cersei was "already dead" when Daenerys decided to rule by fear. Sandor and Arya had a relationship of sorts going on, what he told them just made her realise that revenge just ends up you being dead, and she didn't need to die, Cersei wasn't the Night King.
Greyworm wasn't Unsullied (as a person) anymore, especially after having loved Missandei and her being killed by Cersei in front of him as a "fuck you, Daenerys". When he saw Dany snap, he acted on his anger as well. Nothing out of the ordinary here. Consistent with his story so far, he stopped being a mindless order obeying drone and started evolving into a human filled with emotion.
Cersei beggine, eh, I don't know, got nothing to say here for that.
Jaime always loved Cersei, he always did bad shit for her and to be with her. He realised she could and most likely would actually die this time and didn't want to abandon her.
Northerners weren't saints, and Ned was long gone. They fought the people who were responsible for his death. There's bound to be hate there.