Film techniques - Over the shoulder shot

What is the effect of an over the shoulder shot?
The over-the-shoulder shot shows the connection between characters.

What film aspect shows a disconnection between characters?
When both characters are no longer in the same shot together. Instead, they are in a single close up.

How does the director of this scene show the disconnect of characters?
The director does this by putting the camera on a dolly. While the characters are talking, the camera is slowly moved forward to change the shot from an over-the-shoulder-medium shot to a single-medium-close-up shot. Once they are no longer in the same shot, it means that they are no longer on the same page.

What eventually totally isolates the female character?
Although they are no longer in the same shot, both characters are still connected to the waiter, who is shown on the edge of the medium-close-up shot. She becomes completely isolated when the medium-close-up shot that was facing her changes to a close-up of just her, while the shot facing the male character does not change. This shows that the male character still has a connection with the waiter but the female character is now completely alone.