Here's the problem with the movie and what I think will probably happen:
I think it's going to be revealed that Rey had been trained as a child with Luke and other force-gifted kids before Ben Solo (Kylo Ren) and the CG Orc from the Hobbit killed everyone (except for Rey). Rey is a descendant of Skywalker and/or Kenobi blood. So her quickly discovering these powers and abilities within herself via the force makes total sense, since they're abilities she had already trained and used as a child... just abilities that were blocked away until the events of The Force Awakens. That's the general theory that a lot of people seem to be going with, and it makes sense.
Here's the problem with how they wrote The Force Awakens... that plot line, which will likely be revealed in Episode 8 (if it is legit), totally legitimizes Rey's actions in Episode 7. However, that movie ain't coming out for at least a year and a half. So right now, all we have to go on is what we have to go on.
And that's not good structural writing. This movie needed to be self contained, much in the way that Episode 4: A New Hope was. In Episode 4, the evil empire's death star is defeated, the planet is saved, and the heroes are given medals. However, neither Darth Vader nor The Emporer are apprehended/killed. Further to that, Obi Wan Kenobi is killed. And the empire, likely, lives on. In terms of the protagonist, Luke starts off as a farm boy, struggles with and is trained in the force, and ultimately uses it to blow up the death star. His training isn't complete, Obi Wan's death isn't avenged, but he's a hero.
Episode 7 mirrors this structure in many ways... The evil first order's death star is defeated, planets are saved... there's no medal scene, but that's fine. And like Episode 4, neither Kylo Ren nor Ginger Hitler nor bad CG Voldemort are apprehended/killed. Further to that, Han Solo is killed. And the first order, or at least some form of danger, lives on. That's all kosher. However, Episode 7 decided to go with dual protagonists, and here's where the ball gets fumbled a bit.
Finn's arch is great... or at least the start of it. He begins as a storm trooper trained as a child to kill... and almost immediately rejects it. He rejects the First Order, saves Poe (for selfish reasons), masquerades as a rebel (for selfish reasons), and instead of running away from the first order, eventually stands up to fight it for the good of the galaxy (and, more importantly, his new friends). I like Finn's arch, and I'm looking forward to him evolving (I'm assuming as a fighter pilot/antagonist to Ginger Hitler).
Here's the problem with Rey. With what we know right now (Episode 1 - Episode 7), Rey doesn't have any jedi training. She's a mechanic and scavenger (and is good with a staff), but I don't know if she's even flown a spaceship before Episode 7. She's never held a lightsaber (an off-hand complaint: Finn was a little too good with the lightsaber in his fight with Kylo Ren, but it wouldn't have been a great fight if it was over in five seconds). So yes, Rey has had to struggle to survive on Jakku, and she does have a myriad of skills borne from that life, but... she ain't no jedi.
More importantly, she knows next to nothing about the jedi. About the force. About any of it. The jedi and Luke Skywalker are seemingly myths and legends in her world. Sure, she may have believed they were real by choice, but in terms of knowing the ins and outs of the force... that seems pretty dubious. And here's where the film and its writing falters:
She doesn't learn any of it. It just happens because it needs to happen for her to survive. For the main characters to not die. For the movie to get to the next scene.
Rey hops in the Millenium Falcon and suddenly she's an amazing ace pilot. She exclaims that she doesn't know how she's doing it. More importantly: Rey has not met Han Solo at this point, has not been told that the force and the jedi are real. How is she doing it? I dunno, luck? Inherent skill? It's a kids movie? Whatever, it's fun, and if it was the only instance of this happening no one would think twice about it.
But it happens time and time again. Rey discovers the ability to mind-control a storm trooper. Not only has she never tried to do that before, I don't think anyone's ever told her about that ability. Yet she magically knows how to do it. Rey is also great with a blaster (though so is every good guy, let's be honest), she knows how to force-pull a lightsaber (again, how??) (not to mention her force pull is stronger than Kylo Ren, a Skywalker who's been trained in the arts of the force for years), and she defeats Kylo Ren in one-on-one lightsaber combat. Is Kylo Ren weakened and not in a solid emotional state? Yes. But even so... you gotta imagine he could beat someone who's never held a lightsaber or even used a sword before, force strength be damned.
It wasn't the same for Luke. Did Luke magically know about the jedi mind trick? No. He witnessed Obi Wan do it to a stormtrooper in the first film. Did he magically know how to force pull a lightsaber? No, he'd been practicing and training in using the force beforehand (though I'm not sure how much before he finally did it in that ice cave). Was he magically great at using a lightsaber? No, he was trained by Obi Wan how to use it, and even then he didn't fight Darth Vader in Episode 4... and when he did fight Darth Vader in Episode 5, he put up a fight but eventually lost, got his hand chopped off, and seemingly fell to his death.
That's the rub. All of these force abilities seem to magically come to Rey. It's not just that she doesn't earn them... it's that she doesn't learn them. At least as far as we know.
So, let's say Episode 8 comes out and we discover that Rey was trained by Luke as a child, and the "Awakening" in Episode 7 were her innate powers and training coming to life as the force and the jedi were validated throughout her journey. Does that make sense? Yes! It explains everything that happens in Episode 7! When we're all marathoning Episodes 7 - 9 in a decade, these problems with Rey in Episode 7 won't exist.
But they do exist right now, in Episode 7, as a standalone movie.
You don't have to answer everything in a movie, especially if you know a direct sequel is hitting in less than two years. Especially if you know it'll be part of a trilogy. You need to withhold certain things.
But I don't think they withheld Rey's training properly (if she was indeed trained by the jedi as a child). It's not satisfactory at all because while she is struggling in these fights, she's simply not earning these victories. She's doing amazing things, but there's no sensical explanation how, even when you factor in the magical force. Rey definitely changes throughout the film, she has a character arch, but we don't really know how or why. We just watch her do it.
And again, this is largely built on my guess that Rey was trained in the force as a child. If she wasn't... that's not good. Perhaps Luke was guiding her throughout Episode 7, but that wouldn't really fit in terms of narrative awareness since we, the viewer, are privy to the minds of our jedi protagonists (we see Rey's vision, we hear and see Obi Wan's ghost speak to Luke, etc).
I don't give a shit about Mary Sue labels or anything like that. And despite this rant, I really like Rey and Finn's characters. I think they're fantastic protagonists (and great actors). It's just that Rey's internal journey in Episode 7 was a big narrative misstep. It didn't kill the movie at all, but it did hinder it.
The annoying thing is I think there was a very easy and short way to fix it, but this post feels long enough as it is. I'll post my rewrite suggestion if people are interested.