Well she didn't know everything. Joel never double crossed them, he only did it to keep Ellie alive because she was basically a daughter to him
Yes he did.
The story had problems, but the way you wanted it to go down would have been stupid as fukk. Them just talking it out and forgiving each other would have been WOAT level writing. Everyone knew by the end of the first game that Joel would be killed for his actions and that Ellie would be the protagonist in the sequel. I don't know why some of yall expected some uncharted type adventure with Joel and Ellie.