Grace's Escape by Louise Park

Grace and her mother have moved from Broome to a real-life castle, steeped in literary history, and Grace has discovered that she can slip back in time to previous incarnations of the castle. But this time, when Grace travels back in time, she has to help find two sisters who were supposed to be staying at the castle and have been kidnapped along the way.
 
During her travels, she has the good fortune to meet Beatrix Potter, J.M. Barrie and May Gibbs. It seems the castle has been home to a good many adventures over the years! Now Grace just has to figure out how she and her family fit into the castle’s storied past.