Originally Posted by
eschatological
It's an interesting question, and I think a main difference between TFA and TLJ. I think JJ was going for "She's good by nature, but self-interested in behavior because she HAS to be." That's reflected in the whole idea of rebuffing Finn when he tries to take her hand and lead her away, her insecurities on the Maz Kanata planet where she wants to go home and not join Han's crew (she wants to protect herself), and so on, and so forth. Then, near the end of the movie, you see a true rage in her in her last fight with Kylo, where if the ground between them didn't literally split under her feet, it seems like she was about to go full Dark Side on him. So IDK if JJ was trying to set that idea up, or suggesting it was A Momentary Lapse of Reason (great album, btw). And the only real thing that's changed since the beginning of the movie is that Kylo has invaded (possibly imprinted?) on her mind, and it correlates to a quick upswing in her Force abilities. I genuinely thought that that was a theme JJ was going for, that Kylo actually left some sort of "Dark Side impression" on her.
That kind of gets borne out in TLJ. TLJ seems to imply she's kind of a dick. She berates and won't accept Luke's reluctance to train another powerful Force user, even though he has good reason not to, her understanding of the Force is dangerously simplistic and naive, and, in some ways, all about power, and she (like Luke with Vader in the OT) thinks she has the ability to simply turn Kylo good by sheer force of will. She doesn't resist the Dark Side in her vision quest, whereas Luke was ashamed and confused when he cut off Vader's head in his vision, and saw his own face. She spends a whole movie greedily trying to lap up every powerful super combo she can get her hands on, all while having a literal mental connection to Kylo (supposedly put there by Snoke).....
....and then when Kylo extends his hand for her to rule the galaxy with him....she says no, implying she's a good person. That, to me, was the biggest flaw of TLJ. I thought the logical extension of the movie would be for Rey to fall in some way, and become the new villain. I still kind of hope for it in the new movie. Because nothing between her helping BB8 and her refusing Kylo at the end of TLJ really shows she's a good person.