Seven YA novels with undercover spies

At the BN Teen blog, Jenny Kawecki tagged seven YA titles with undercover spies, including:
Orphan Monster Spy, by Matt Killeen

When Sarah’s mother is shot at a Nazi checkpoint as they attempt to escape Germany, Sarah is rescued by British spy Jeremy Floyd. Realizing petite blonde Sarah looks more Aryan than Jewish, Floyd takes her under his wing and gives her the opportunity to infiltrate a