Melody Pond (Prequel to The Impossible Astronaut)

This girl contacted Richard Nixon for assistance, but he did not know who was calling him. She told him about the "Monsters", and how she feared them. She told Nixon the words "Jefferson Adams Hamilton", leading Nixon to believe she was a boy, but the Eleventh Doctor helped them to discover that these were the names of street names, the only three in the same place together in Florida, and probably all of America, according street names and the only place these were together was Florida.

The girl later encountered the Eleventh Doctor and Amy Pond. To prevent a future in which the girl killed the Doctor, Amy fired a gun at her. She dressed in an American astronaut suit. (DW: The Impossible Astronaut)