very cute. looks like she really likes tennis.
Have her hold the racquet in both hands longer. currently she is letting go with the left hand too early and bringing the racquet back with one hand.
This will lead to errors and 'break down' during rallies because under pressure that right arm will move back at different speeds/degrees each time.
She should hold with both hands on the racquet in front of her body. Then rotate the trunk while still holding with both hands and the racquet still in front of her torso. (unit turn) Then when the left hand reaches to about the right shoulder she can let go with the left, extend that left hand out and drop the racquet w/ the right hand.
Like this: http://www.youtube.com/watch?v=1ImeQaAyFPc