how about the old fashioned way; when around a lot of people & the liar lies, tell everyone the truth that the person just lied, is a pathological liar, has been lying for years & he or she, needs to be correct right on the spot without hesitation!. liars can be highly conditioned to response from a developement in early childhood & never grow out of it. immediate correction is something that has traveled the "wind race" & got lost. remember the verse in which Jesus says tell the brother a correction, if he won't listen gather another & if he still won't listen, have nothing to do with him? & finally, pray for that person.
Again I ask - What if you cant walk away from them and its your wife? or your husband? What if there isn't a reason for divorce, and you have to be with them, sleep with them and be intimate with them because scripture demands it?
What if its a parent and you are too young to pull away from their authority yet. You have to put up with it day in and day out, never being able to believe a word they say?
I think that is so so hard to imagine living with. And so so hard to counsel anyone in such a tricky situation if taking to them doesn't work, or if trying to out them back fires, and then just makes the situation worse at home. Yeah I still don't know what to advise someone in that situation and I do know for certain that there are people in just such a situation sadly. Whose daily life is one of gas-lighting, second guessing and never being able to take anything as real or true from someone so close to them.