By the original definition of an author insert character Bella is absolutely one.Bella is a Mary Sue?
She doesn't seem to have the power to be. She has a ridicilous overperceived importance in the Twilight world, but I don't really see that as an exact clarifier that they are a Mary Sue. Bland character? Yeah.
About Rey,
I see using the Force like being able to access a Gamefaqs faq about what to do in a game when everyone else doesn't have one. When Rey finally closes her eyes and let's the force in, it basically guides her on what to do. Same thing with the Skywalkers and their impressive feats with technology. Anakin had the pod racer, Luke had the X-Wing, and Rey has the Millenium Falcon. The force guides them on how to do these things, even if they themselves aren't aware of it.
She physically resembles an idealized version of the author, has a mysterious unexplained power, and hot dudes are willing to fight to the death for her.