Hesse, Karen "Letters from Rifka" - 1992
I picked up this book at a school book fair because it looked quite interesting. The story is told by Rifka, a Jewish girl who has to leave the Ukraine with her family to go to America. On the way, she gets sick and cannot go with the family but has to stay behind in Antwerp. She writes down imaginary letters to her cousin in the margins of a Pushkin book and that way we learn about the lives of the Jews in Eastern Europe and the troubles they had to go through in order to get to lead a decent life.
From the back cover:
"In letters to her cousin, a young Jewish girl chronicles her family's flight from Russia in 1919 and her own experiences when she must be left in Belgium for a while when the others emigrate to America."
The novel is recommended for 9 to 12 year olds but I am sure it is still interesting for older teens.
I also recommend "Out of the Dust" by the same author, about life during the Great Depression.