The only one responsible for what Snow have done to Cora is none other than Cora. Cora who wanted to become the new Dark One. Cora who sent Hook in Manhattan. Cora who tried to kill all the Charmings. Cora who was about to kill Rumpel.
What do you think seriously? If you where Rumpel wouldn’t you want to do anything to avoid dying? Wouldn’t you trade your life for the one of an evil witch who want nothing but kill everyone to gain power including you? What would you do? Ask yourself this and answer in all conscience, with sincerity, what would you do?
And Snow isn’t responsible for Daniel death, I’m tired of people holding this against her. She was a little girl. She was naive, she was a child who choose to trust an adult. Cora and Cora only is responsible for Daniel death. End of story.