In case Star Wars sequels, Rey as Mary Sue topic. No she is not.
Why you would need to compare her with actual Mary Sue character from recent sci fi.
Michael Burnham from ST Discovery is mary sue.
Rey is just main character (may not necessary as good done as she should be) in movie saga centered about chosen one hero, all aspect of her character are required, even her possible family connection to other characters was something what fans actually want and its typical thing for SW anyway. Meanwhile Burnham is chosen one hero who is center of plot and even setting of new show in franchise what don’t do chosen one character (Sisco was technically one but not in this sense, it never overshadows entire DS9) or even main character at all being more of ensemble shows with focus more equal on crew (or even beyond crew like in DS9). Also Burhman is previously unheard off adoptive daugher of Sarek and sister of Spock, human raised as Vulcan and even keeping up with or exeding other Vulcans in their fields, this scream more fanfic character than character being girl and following some of Luke footsteps.Rey despite her status still gives more room for other character to breathe, they can have their own stories, actions and rey is not required to solve everything while also everyboy around her is sucked out of competence unlike Burham. In short Rey doing her job as main character of Star Wars story while Burnham warps Star Trek story around herself.