The Paris Housekeeper by Renee Ryan

From the author of The Secret Society of Salzburg comes a powerful and moving story of bravery and resilience in World War II Paris and one woman who must face impossible choices to survive ...
Paris, 1940
German tanks rumble through the streets of Paris, forcing frightened citizens to flee. But not everyone has the luxury to leave. Camille Lacroix, a chambermaid at the world-famous Hôtel Ritz, must stay to support her family back home in Brittany. Desperate to earn money, Camille also acts as a lady's maid for longtime guest Vivian Miller, a glamorous American widow-and a Nazi sympathizer.
Despite her distrust of the woman, Camille turns to Vivian when her friend and fellow hotel maid Rachel Berman needs help getting out of Paris. It's then that Camille discovers that Vivian is not what she seems... The American has been using her wealth and connections to secretly obtain travel papers for Jewish refugees.
While they're hiding Rachel in an underground bunker under a Nazi's nose, a daring escape plan is hatched. But as the net grows tighter, and the Germans more ruthless, Camille's courage will be tested to the extreme...
"Renee Ryan is a brilliant storyteller."
-Madeline Martin, New York Times bestselling author of The Librarian Spy