Have you watched the show Haven on SyFy? Its based on Steven King's novella The Colorado Kid.
This could be a good inspiration. Of course if you replace "Supernatural powers" with "Aliens in disguise", and it would be reminiscent of "They Live" plot. As well, the "memories may not be her own" could play into the amnesia part. Not mentioned here, but the citizens of Haven aren't allowed to leave town(unless cast out to die) to prevent the outside world of learning about the "troubles", and there is a generator that has to be kept running to keep away "the darkness".
From Wikipedia:
When FBI Special Agent Audrey Parker is dispatched to the small town of Haven, Maine, on a routine case, she soon finds herself increasingly involved in the return of "The Troubles", a plague of supernatural afflictions that have occurred in the town at least twice before. With an openness to the possibility of the paranormal, she also finds a more personal link in Haven that may lead her to the mother she has never known.
Over time, Parker, who has quit the FBI to join the Haven Police Department, begins to realize that her arrival in Haven may have been pre-arranged and that her name and even her memories may not be her own. As the series progresses, she learns more about the mysteries of both Haven and her true identity.
She and her partner, police detective Nathan Wuornos, find themselves frequently facing problems caused by both the effects of the Troubles, as well as the activities of town folk who take more drastic measures against those who are Troubled.