Kayla Knowles

Kayla is a daughter of Apollo. She was with her siblings and the rest of the Campers in The Battle of Manhattan in The Last Olympian.

The Last Olympian
Kayla is among the Campers that go to New York City and fight for the Olympians. She and her half-brother Austin set traps along the Brooklyn Bridge with their half-brother Michael Yew directing them.

Kayla probably survived, and was commanded by the new cabin counselor Will Solace, her half-brother, to look for Michael Yew. Michael's body was never found, and he most likely died as this seemed to be the general opinion at the memorial ceremony and Percy only saw his bow and presumed that he had fallen into the river below the Williamsburg bridge. He never came back so it is probably safe to imply that he died.