The war between the Republic and Empire never really ended with the death of the Emperor, no matter what the history books say. And Vader was never the last of her kind, just the harbinger of new, darker players. Step one foot off the main trade routes, and you'll land in one of a hundred brushfires stoked by the two great furnaces, with some kind of Vader wannabe on the side of the oppressors.
Ellaita is involved in one of those so-called minor conflicts, though how minor it really is when there's an entire sector and multiple fleets of starships in the mix is debatable. She's part of a resistance group, for all the good they're able to do against the enemy's seemingly endless legions of stormtroopers. The troopers' commanders call themselves the First Order, they're lead by a guy with a red laser sword and blah blah blah. That's not important. What is important is that they're looking for a weapon, and she's going to beat them to it.
She doesn't have a fancy laser sword or any mystical powers. What she does have is an X-wing, a keen ability to fly it, and intel that what the First Order is moving on Jakku as the next stop in their hunt. She's going to get to Jakku first, find the weapon, and use it against the First Order.