Answer :
She is afraid of becoming too close to someone and then leaving them when her cancer gets out of control.
The main conflict in the book is cancer. Hazel's cancer impacts every decision she makes in her life. It's the reason she is scared of becoming attached to people, especially since she knows that one day she will die. It affects her when she almost doesn't get to go to Amsterdam. It affects her when she meets Augustus. She is limited, because of her cancer, although she tries to do everything she can. It also affects Augustus when his cancer comes back.