Jane Gallagher is an interesting character in The Catcher in the Rye, as she never appears in the actual timeline of the novel. Despite the fact that Jane is not in the current timeline, she is immensely important to Holden. What we know about Jane is limited to what Holden Caulfield tells us in the story, but we gather some information as to where she lived and is currently living. From Holden, we know that Jane originally lived with her family on Cape Cod before moving to Maine. Once the Gallagher family moved to Maine, they lived in the same neighborhood as the Caulfield family. While in Maine, Holden and Jane bonded, and he talks about this throughout the book.
Jane is a character that Holden actually has immense affection for. One gets the sense that when the two go off for prep school, Holden is distraught about the fact that he has not heard from Jane. It is stated that Jane is at Shipley, but she says that she might go to BM earlier in the text.