I also have someone in my life that constantly lies—my mother. She does it to everyone, and I don’t have a good explanation for it. I think she lies for sympathy, to make herself look better, or even just out of habit.
Calling her on the lies is extremely tempting. Sometimes I literally have to bite my tongue. I do a lot of eye rolling, or put the phone down (she lives several states away) and take a deep breath. I used to question her and point out inconsistencies in her “stories.” She would only try to cover it up with more lies, get angry, start to cry, and throw a guilt trip at me. We’d have long, frustrating arguments on the phone that never accomplished anything. Finally, I decided to just give up and stop trying. She will never change, and I can’t just cut her out of my life because she is my mom. I make good use of caller ID and vent to my husband.
So, you have to decide if it’s worth it to call someone out on their lies. Is it a family member you can’t avoid? A coworker? Sometimes I’ll still say something to clue my mom in that I know she’s lying, but it doesn’t seem to make any difference. You could try giving a hint here and there to let this person know you’re aware of the lies, but if this is someone that you, for whatever reason, have to keep the peace with, it’s probably not worth fighting over.