I think we need to put more light on this.
Definition:
Gaslighting is the manipulation of someone into questioning their perception of reality.
Let's talk about that definition first, because there's already a trap built in.
Imagine a person that has been manipulated so they can't see reality anymore. I don't want to go into details about how it works, just that it is based on the psychological effect of dissociation. The MK-Ultra stuff. Traumatize a person until you can shape their mind to your liking.
If you now want to heal that person, you have to question their wrong perception of reality.
This means that every attempt of disclosure or exposure to truth can be framed as gaslighting. The person is being confronted with new information that don't fit into the worldview the person is used to, and that always feels like a negative thing.
So, gaslighting is like the evil brother of disclosure. Just keep that in mind.
The purpose of gaslighting:
The purpose of gaslighting is to obstruct by confusion.
Imagine a person doing something wrong. You tell that person that what they are doing is wrong. The term "wrong" just means that the expected consequence is not the same as the actual consequence. So, the intention of telling people that they are wrong is to achieve a change in behavior, such that the expected consequence matches the actual consequence.
This is not a problem at all if the person doesn't know that they are wrong AND is open to look at it and change it.
It becomes a problem when the person knows that they are wrong and want to do it anyways, or when the person is not open to the possibility of being wrong. In other words: The ego wants to be correct despite evidence that it's not.
Now imagine such a person. You are telling them that they are wrong. They don't want to be wrong. They want to proceed with their behavior, ignoring the possibility of harm. Maybe they even want to harm you.
How gaslighting works:
Gaslighting now consists of the following simple tactic: When somebody tells you that you are wrong, tell them that they are wrong. It doesn't matter whether it's true or not. Just pull something out of your ass. People are not perfect, everybody makes mistakes. Remember an arbitrary mistake and make that the center of the dispute.
That way, the initial accusation is being pushed in the background. The conversation frays out, until the one who wanted to solve a problem doesn't even know anymore what everybody is talking about.
As you see, the goal is to not solve the problem.
Solution:
Just keep track of the initial argument and keep coming back to it. Insist that there's a problem that needs to be solved. Provide evidence, or logical proof, if you can.
The gaslighter will shift gears and accuse you of more and more horrific stuff. Let it reach a point where it gets so absurd that everybody can see who the crazy one is. At that point, the solution is to end the relationship. Exercise your right to dissociate yourself from that person.