The Twilight Zone (1985) - A Message from Charity

In this adaptation of a 1967 short story of the same name, a sixteen year old boy in 1985 forms a psychic connection with a Puritan girl of the same age in 1700. Over the course of 40 minutes, two characters who never appear on screen together share every moment of their lives with each other, giving advice and emotional support, forming an intimate friendship and a little more.

If this had been written today, I would say it was obviously about online friendships, especially the way it can be more vulnerable with people we don't know in real life and the way that those of us stuck in conservative places look up to people who live in places where the grass is greener.