So Poe was given the Falcon, not an X-wing, because the ship is a piece of junk and works perfectly for an undercover mission. was sent on a mission by Princess Leia to go to Jakku to follow up on a report of a found light saber pertaining to belong to Luke, or they made that assumption since not many people in the galaxy own light sabers.
I think she's stranded for whatever reason, and doesn't have a ship or the means to get off the planet - hence her emotion when seeing all that green (MSW?). She's living in a downed AT-AT in the middle of nowhere.
