Who is Brett Messerschmidt from The It Girl and what is their importance?

Brett Messerschmidt is the roommate of Jenny and Callie at Waverly Academy, is beautiful, and is keen on difficult love. She is currently in a relationship with Jeremiah, star quarterback for Waverly's rival school, St. Lucius. Brett also begins an illicit affair with her adviser and teacher, Eric Dalton. Brett harbors suspicions that Callie has something to do with the expulsion of their friend and previous roommate, Tinsley.