Tiara Gold is the true main antagonist in High School Musical 3: Senior Year.
Role in the film
She is a foreign exchange student from London who goes to East High where she meets Sharpay Evans. Tiara then asks Sharpay if she could be her assistant (after Sharpay put posters everywhere) and Sharpay agreed. She shows interest in musical theater but tries not to upstage Sharpay until later. Later on in the movie she is made Sharpay's understudy and Jimmie and Tiara fight. Tiara overhears Gabriella telling Taylor about her going to college early and tells Sharpay. After being humiliated in the stage Sharpay arrives to see that Tiara was wearing her costume. Tiara then tells her that she is from London School of Dramatic Arts and that next year it will be her drama department and that she was just acting all along. When Tiara begins performing "A Night to Remember", Sharpay crashes her performance. Ms. Darbus later announces that next year Sharpay will be helping in the drama department and Tiara angrily smirks.
In the deleted scenes, it is revealed that after Sharpay graduated, her locker was Tiara's. The locker was the same, with the exception that the locker had the British flag on it instead of Sharpay's pink one.