If a heroine is especially good at anything, even if it’s just one thing and she’s spent years working on that skill, she may get called a Mary Sue. If she’s a relatively well-balanced individual without PTSD and a string of broken relationships and powerful enemies hunting her from the get-go, she may get called a Mary Sue. If there’s anything about her life that you would enjoy in your own, she may get called a Mary Sue.
In short, if she’s the protagonist of the story and there’s anything admirable about her, then to some readers, she’s a Mary Sue.
Marie Brennan, “Who Mary Sue Isn’t” (via nonisland)
