How do you deal with a disingenuous person,

[cilla4progress]

that is to say - a liar?

[abqtommy]

1. The same thing that worked for me when I was a 4th grader still works for me at age 72.

I just say "Liar,liar, pants on fire. Nose as long as a telephone wire".

[Throck]

2. Too early to discuss Thanksgiving dinner with my relatives.

[FakeNoose]

3. It helps to record everything they say

... and play it back at the appropriate time. Like when they just contradicted themselves.
But I recognize that it's a little awkward doing that.

Try trusting your memory, remind them what they said to you in the past. See if they even acknowledge that they said something different before.