glass castle question

Jeannette resolves to leave Welch after classes end to join Lori in New York City. Her father tries to entice her to stay, promising to resume work on the Glass Castle but Jeannette tells him not to bother building it for her sake; she is leaving Welch even if she has to walk to New York City. Rex walks his daughter to the bus station to see her off and he gives her his favorite jackknife for protection.