The answer to this question is subjective and left up to individual readers. You can answer either way and defend your response:
No, Cinder should absolutely not have gone to the ball. She knew it was a risk to go there in the first place, and she knew that her chances of giving Kai the information were slim. Cinder risked losing far more than she might have gained. Her eventual arrest and imprisonment prove that she should not have gone to the ball. Her best option was to distance herself as much as she could from Kai and Levana in order to protect herself.
Yes, Cinder most definitely should have gone to the ball. Cinder has a moral compass, and going to the ball was the right thing to do. If Cinder didn't go to the ball, then she would risk living with the guilt of knowing that she could have made a difference for her friend Kai, for her government, for her country, and for possibly all of Earth. Cinder doesn't desire to be a hero, but she does desire to do the right thing. Going to the ball was the right thing to do; therefore, it was worth the risk.