That way you don't have to remember what you said." ~ Mark Twain
"How do I handle it when it seems someone else is not telling the truth, especially when I address it and it is denied?"
The best any of us can do is to be authentic, live with integrity, and focus on ourselves.
If there are people in our lives who are inauthentic, it's a great opportunity to explore what role or purpose that person has in our lives. In some cases, it's also helpful to look at how they may be reflecting back certain aspects of ourselves or our lives where we might not yet be living 100% authentically.
And to be clear, this isn't a criticism or necessarily a "bad" thing. It's true for ALL of us, including myself.
The path of personal growth, the pursuit of Truth, means that we are consistently noticing areas where our inner worlds and outer worlds are not matching.
It's in reconciling those differences, without judgment, where our greatest and most profound opportunities for growth will be found.