I'm fine with Rey coming off like a "Mary Sue" even if I don't think she is because we're only seeing act one of a three part play, her mechanical and piloting ability could be inherited or part of the "will" of the force. We don't really know much about her really she and Kylo Ren kind of come off as opposite sides of a coin Rey is light side Anakin (and Luke) minus his issues while Kylo is dark side Anakin with all his issues and a lack of the restraint Anakin learned along with some of his own while barely or poorly trained. Going by Wookieepedia's sources Rey is 19-20 (another Luke parallel) while Ren is 29-30 so there's around a 10 year age gap between them, do we know when he turned and how long he was under Luke's guidance?
If by episode eight we find out she really is just an orphan with no ties to anyone significant then I might have an issue, especially with the force manipulation but I assume it's because of a powerful lineage and a borrowing of KOTOR plot points and if that's the case I'm totally fine with it. I can enjoy "oh shit" level game changing good guys (like Neo from the Matrix, especially when he became "The One" or well, Superman) but I really don't see it ending that way once Kylo Ren gets his head screwed on straight.
But breaking his force hold and proceeding to whip his ass once she remembers to use the force does make it clear who is more powerful right off the bat. Ren has been at this for years and gets bested by somebody who just tried using the force for the first time like 15 minutes ago.
Sidebar: the theory that Kylo's sword play is weak because there are no Jedi for him to go against gets thrown out the window by him losing the force hold battle with Rey. At first I thought well maybe Kylo is stronger in force holds and chokes because he likes to torment people but Rey even broke his holds like it was nothing.
First time that we know of and Rey remembers. Ren has several handicaps at that point and is unfocused, even the dark side of the force needs some level focus to properly wield, its reliance on emotions is also a weakness as it was in Ren's case and Anakin before him.