Juvenile fiction set in Europe during or shortly after WWII, read in the early 80s, probably published in the 70s or 80s.

[Marianne]

I read this book sometime in the early 80s and I may be combining two books. The main character (female) has an older sister and possibly a brother. The older sister is very determined. She wants to be a writer, so she moves away to Hollywood and near the end of the book we find out she has become a TV writer. We might find this out through a letter. I feel like the book covers several years, and the characters grow from late childhood/early adolescence to young adults. Someone is named Marta, but I can't remember who. I'm pretty sure the family is Jewish or at least lived in Europe during the Holocaust.