No and we don't need a thread for this it has been discussed before in other threads.
1. A lot of people (including yourself) don't understand what a "Mary/Gary Stu" are. They are really avatars for fanfic writers where they instill themselves into the character being perfect and never doing anything wrong.
2. Rey is a hero with lots of strong traits, but she is massively flawed as well. People act as if the only way to not be a "Mary Sue" (let's not lie here if she was a man no one would bring up anything) is having it where she murdered her own brother and sulks in the corner having "complexities and depth".
3. She has many flaws
-She is somewhat of a coward to begin with and afraid to face the journey/call to the gods. Even more so than Luke. She is afraid to leave Jakku, she has a fools hope that she will be rescued by her family. This one single thing is enough for her clearly not be a Mary Sue. But there is more multiple times she runs away, out of anger/fear.
-She gets mad at Finn and pretty much runs away again from it all when Maz attempts to give her the lightsaber. She flees wanting to run away again from it all, being somewhat of a coward.
-She is captured, failing to run away fro Kylo Ren, is captured, and "mind raped". Again huge things that stray away from a Mary/Gary Sue.
-She is beat to crap by Kylo when he flings her across the forest.
-Many don't notice the flaws of her because they don't focus on them straight up. She admits she has flown ships before. But when she does fly the Falcon it's far from perfect. I truly desire for people to watch that scene again slowly and see how many times she is scraping against the debris and hitting the sand very clumsily. But even still she has had practice and said so, just as much as Luke did and took on the Death Star.
-During the duel at the end, really watch her before the end. She is falling to the ground clumsily lunging at Kylo while he toys with her. It's not until the Force flows through her at the end that she finally bests the heavily wounded Kylo Ren.
-She is also clueless about many things and clearly not worldly.
-There is many explanations for the things she's good at. She's a scavenger that has survived on a harsh world unlike Luke for years by herself and having to fend off enemies with a staff, clearly having some skill in melee combat. Her mechanical prowess is because of her being raised around nothing but scavenging technology and having to survive with what little she had. Being surrounded by other aliens her whole life having to learn different languages to survive, not uncommon even in our world. Most of the things she's good at are mechanical in nature because all she's done is strip spaceships and advanced weaponry all her life, so it would make sense for her to have quite a bit more knowledge then most.
Now she is a great hero, and has higher abilities than any of us normally would...but that is a hero. That's what they are. They are what we wish we could be. You knew Luke would make it too, as much as Batman, or Spider-Man. There are obvious heroes and 99% of the time the hero does not die and makes it.
Lastly regarding Star Wars lore, like Luke before her she is imbued with the Force, in a special way even beyond other Jedi. In a deleted line of dialogue (probably to save more for VIII) Kylo Ren even says "It IS YOU!" at the end duel. Much of the movie clearly shows she was being trained somewhat as a Jedi early on and has a very natural gift with The Force. And hence the title "The Force Awakens." If you notice it's when Kylo "Mind rapes" her that something is clearly unlocked and that's when she starts using the Force in an outward way like the Jedi Mind Trick.
So your "feeling" that she would always get out of it, is clearly a mis-understanding on what "Mary/Gary Stu" actually is. And even beyond that point she clearly is not. She's actually one of the more favorite parts of the film, even to those that did not care as much and was loved for her depth and connectivity to the audience. But all major heroes you know will make it. I will give you a hint she will in VIII too.
JJ's actually best part of writing in TFA was Rey, she was just an amazing character and clearly someone that has connected with the audience and people want more of her. Gary/Mary Sues actually rarely do that because we want flaws in our characters. But they don't have to be gaping "I killed someone and hid the body" type of flaws.
