At the beginning of this section, Winnie is very skeptical of her situation. While she is interested in Jesse, she is scared of being involved with his family and feels worried over her own situation. She feels trapped and has essentially been kidnapped as they are all running for their life (metaphorically, since the Tucks cannot die).
However, at the end of chapter 18, Winnie has grown close to the Tuck family, seeing them almost as her own surrogate family. They are kind, caring, and deeply loving. While she is still afraid, she has come to the point where she will stand up for any of them and will do whatever she can to keep the Tuck family's secret safe, even risking her own life by taking Mae's place in jail.