She was the hero that saved the world, so it's kind of weird to say she has main character syndrome when she actually lived a life much like a main character of a story.
She can't be living a delusion if the things actually did happen. Plus if you're living a delusion cooked up by someone of higher power, that delusion is still your reality so...."unknowingly living a fake life" would be the closest thing and even that doesn't apply to her since what she lived was very much real.