The Question and Answer section for Divergent is a great resource to ask questions, find answers, and discuss the novel.
Tris feels that choosing another faction, she has abandoned them.
This question has no right or wrong answer and calls for your opinion. I, myself, would not want to live in this society. I prefer freedom and the ability to choose my own life.
Four told her to do this because he wanted her to walk in there as if the attack didn't bother her.