In the book, Beatrice questions her morality and her general thought process because it does not follow the code of abnegation (which is her faction), because of that fact she questions whether it is a wise choice to leave abnegation. The upcoming aptitude test determines what factions are best suitable considering your traits, and everyone that is 16 has to take it, including Beatrice and her brother. Beatrice's aptitude test results are inconclusive and she is told by her administrator that she is divergent and she shouldn't tell anyone ever.
I don't want to help this kid.
"it is on these mornings that I feel guiltiest for wanting to leave them."
No knife or cheese
After thinking all night Beatrice is conflicted but knows what she is going to do at the ceremony. Beatrice chooses her new faction, she feels bad for leaving her family and questions her brother for leaving because she views him as the embodiment of the abnegation code. She is a part of the dauntless now trying to find a place where she belongs. Marcus reveals background on the factions and adds onto the world building.
Pick your new faction!
Over the course of her dauntless training, she feels at home and the view on Beatrice's morality begins to change. She begins to accept her personal desires but struggles with choosing to be brave or selfless. Beatrice worry's that her divergence will get her killed but later on she accepts it and realizes that she can be both brave and selfless. What Beatrice will figure out is that her divergence is an asset and will save her.