Episode VII (spoilers)

[Drich]

I think she's one of Luke's students that escaped Kylo's slaughter of the padawans. She was dropped off at Jakku to be hidden away. That being said, she could still be Han and Leia's daughter; when they were talking to Maz she asks Han who she is, then we cut to her finding the saber and Maz shows up and knows a lot more about her. Han must have told her. Or it could be she's an unrelated student that Han knew about, or maybe he pieced it together after being with her for a while.

Well, who was she so steadfastly waiting for?  It must, we'd believe, be her parents, and we know that Luke has been in self exile.  Could it be that Luke secreted her away, much as he had been with his aunt and uncle, to keep her safe?  Could it be that when she looks up to find Luke, who she knows as a famous name, it's her father standing there, and she'd known him by a different name?

That would seem too obvious, but it also seems pretty likely to me.

On a different subject-- did everyone else notice that Han Solo called his son "Ben," as in Ben Kenobi?

Yeah my wife said leigha probably named him because of her connection/respect she had for him in a new hope.