She's a know it all. She can't stop herself from ipinapakita off how much she knows, despite how it makes her unpopular.
She can also be narrow-minded, as seen sa pamamagitan ng how she treats Luna's beliefs and how she dismissed the idea of the Deathly Hallows really existing.
In Halfblood Prince, she was jealous and didn't deal with it well at all. However, I don't think she's shown this particular flaw in other books.
