The music playing at the end when Diane looks back at the ballet company is Tchaikovsky's Serenade for Strings in C Major, Op. 48, II. Valse.
At the 7:58 mark Cliff Is checking out the chest of his fellow actor instead of watching Diane's dance video.
Diane's wistful, backwards glance at the ballet dancers at the Boston Dance Company is reminiscient of Sam's gaze out of the hospital window in episode Dark Imaginings.