Saving Mrs. Roosevelt: WWII Heroines

Shirley Davenport is as much a patriot as her four brothers.  She, too, wants to aid her country in the war efforts and joins a new branch of the Coast Guard for single women called SPARs.  At the end of basic training, Captain Webber commissions her back home in Maine under the ruse of a dishonorable discharge to help uncover a plot against the First Lady.  Shirley soon discovers nothing is as it seems.  Why do the people she loves want to harm the First Lady?