Stubborn and moody kid

 My daughter is in IInd class. She grasps things quickly, remembers well, corelates things but all this goes to drain once she becomes moody. In seconds she changes.If she is studying , gets a thought about T.V thats it to motivate her again to study becomes a tough task. I have to keep on repeating study... How can I make her realise to do her work.She doent like to be pointed out. Sensitive Parrot repeats what we say to her. If I raise my hand she doent hesitate to lift hers. I need help.