Here we are, to the big question-- is our dear Sophie Foster a Mary Sue?
These are my thoughts, of course, and feel free to disagree with me-- but I'm just going to get this out of the way right here and right now: I think Sophie used to be a Mary Sue, and now she's gotten better.
Okay. I said it. Now let's get into the reasoning.
Based on the article I shared above, I will be using 5 warning signs of "Mary Sueness," and then quoting lines from the Keeper series to back up my opinions on each sign.