Anya of Mars Series by Martin Berman-Gorvine

Trapped in the Warsaw ghetto in 1942, teenager Rachel Zilber escapes the horror by writing about the adventures of Zap-Gun Jack and Princess Anya of Mars. When her parents are captured by the Nazis, Rachel's transported into her make-believe world, but the danger is far from over. Together with Katie, a girl from the future, Rachel joins Jack and a rag-tag band of misfits to fight the evil Lord Ares III of Mars and restore Princess Anya to her rightful place on the Martian throne.

Life is never dull when you've created a new world or two! After restoring Princess Anya to her throne on Mars, Rachel, Katie, and Jack return to Venus to rescue Sonia, Katie's adopted sister, from the clutches of Da Mayor. With the help of Jack's brother and his friends, they also fight to free the inhabitants of the oppressed city... moreLife is never dull when you've created a new world or two! After restoring Princess Anya to her throne on Mars, Rachel, Katie, and Jack return to Venus to rescue Sonia, Katie's adopted sister, from the clutches of Da Mayor. With the help of Jack's brother and his friends, they also fight to free the inhabitants of the oppressed city. But Da Mayor can change the future and even erase Rachel from the world she created! Can Rachel and her friends survive long enough to overcome Da Mayor's evil plot and save the lives of everyone on Venus? Or is the planet doomed to return to a scorching, sulfur-filled death-trap, killing all who live there? less