The Enemy's Daughter, by Anne Blankman

At the onset of the Great War, twelve year-old Marta and her father are caught overseas in America and must undertake a dangerous trip under false papers to return home to Germany.  Unfortunately, they choose to cross the Atlantic aboard the Lusitania and when that boat is sunk by the German Navy they narrowly survive.  On land, her father is arrested as a suspected spy and Marta flees.  Alone but sharp-witted, Marta finds her way to York where she befriends an Irish girl whose family gives her a home.  But with all Germans considered to be dangerous enemies, Marta must conceal her identity.

Torn between her love for her country and the undeniable cruelty of the German navy in sinking a civilian ship, Marta still believes that Germany is in the right.  But living amongst the English for several months, she begins to wonder if it all isn't a bit more complicated than she's learned in school.  Her Irish friend hates Germans as fervently as she hates the English, yet the two girls have nonetheless become best friends.

A lovely adventure, but with a glacial pace and the repetitive storytelling.  Its two themes ("there are no sides" and all people can be good or bad) are well-established and then driven home in again and again.  Those are fine messages but become boring in their repetition.  Some of that is of course the story's limitations.  The premise is interesting, but there isn't very much that can be done with the character.  There's only so much adventure that one can plausibly subject a twelve year-old to in a middle reader.