??? You can say she's sorely mistaken...blind to the truth, etc..
But calling her a "LIAR", imo, is a bridge too far.
That's all... 
I prefer “being so invested in a narrative that it’s difficult to change one’s mind even when exposed to new information”

If you read my posts from earlier, I mentioned some left-wing relatives who insisted that Donald Trump called the Charlottesville neo-Nazis “very fine people.” Even when I showed them the whole transcript, they still insisted it was true
Those are the things that get frustrating but there’s nothing you can do about that. That’s why sometimes you have to stop and reel it back a little and just tell yourself you can only present facts and information to somebody but you can’t make them believe or accept it
Have I been wrong on something in the past? You bet. And it is hard to admit it. But if the individual that’s corrected me is able to back up their case, I’ll acknowledge my error, if at least privately