This particular scene works best in understanding what “gaslighting” is. It also shows the moves of a pathological liar in motion. When watching this, pay particular attention to when she says “the letter.” See how Gregory stops in motion, is thinking, then turns around and stumbles with his words ever so slightly before conjuring up the lie that she never had the letter in the first place. When Paula uses the terms “insane” she is letting us all know that this is what it feels like when someone is gaslighting you. Although she says “Are you trying to tell me I am insane.” This is an educated woman trying to make sense of her reality. This is the difference between a lie an gaslighting.
At the end, a discussion is had about why “he” can’t let her go out in public. This would have been the worst thing that could happen to a society woman in her time period. She would become speculation for gossip and rumors, which we see in this movie when the two maids are talking outside the house (this is not on this clip). In today’s day and age, if a celebrity couple is captured in a photo (alone or together), perhaps in a bad mood, bad hair day, poor choice of clothing, this is the modern way of “going out in public” and gossip and rumors run havoc in the tabloids.