Rachel was excited to meet Chaya because she is from the big city.
When Hannah is magically transported back in time, she becomes Chaya. Rachel thinks Chaya is on her way from the big city of Lublin, where her parents died as a result of a cholera outbreak. This kind of thing was not uncommon in big city ghettos where Jews were forced to live before and during World War II. Clearly where “Chaya” is from is important to Rachel. You can tell this by what she calls her—“Lublin Chaya.”
“So—you are Lublin Chaya," the girl said, her voice catching strangely in mid-sentence. Before Hannah could deny it, the girl had threaded her arm through Hannah's, calling out to a knot of girls who were standing by a newly arrived wagon. "I have found her, Lublin Chaya." (Ch. 6)
Hannah/Chaya is not all that impressed. She is so confused and disoriented by the whole thing that she is almost downright rude. She keeps insisting she is from New Rochelle and saying that she already has a best friend. Soon, however, Rachel’s enthusiasm wins Hannah over and the longer she stays in the past the harder she finds it to keep the barrier between her Chaya self and her Hannah self. She becomes more and more Chaya.
Chaya entertains Rachel with plots from movies and books, and the girls become friends for real in the days leading up to the trouble. Hannah almost forgets the time period she has been transported back to, and what is about to happen. There is not much she can do, of course, and no one believes her. She has availed them of so much fiction that anything she says is just more fantasy. Stories of Nazis and concentration camps, and the real danger they are all in, are bound to fall on deaf ears as just the plot to another movie.
In this interesting piece of historical fiction and time travel, Yolen crafts a tale of a girl who doesn't quite fit in with her own world. When she somehow finds herself in the past, she understands her family history in a way that she never could, and perhaps never should have had to.