why lie to the point where you're lost in your own lies??

I don't know if you know any compulsive liars, but I've encounter plenty in my life! The funny thing is I had an argument with one the other day. We were arguing about something she said to me that came back to bite her in the ass. So she tried to defend herself by telling me what she "actually" said. When she started talking, I couldn't help but to ask myself, is she serious? I mean she was completely lying right in front of my face about everything she said. The only thing I could do is laugh. Then I tell her she's liar and everything she's saying is a lie. As soon as that happens, she gets really upset and starts crying. That was either a defensive move or she's really emotionally hurt that I don't believe her. If she really thinks she's telling the truth? She had to have lied about saying so many things that she must've lost track of what she said. It made her look foolish and I would never want to look like that arguing with someone to get my point across. So save yourself some dignity and foolishness by not lying to the point where you're lost in your own lies. I mean we shouldn't lie anyways, but lying sometimes is apart of everyday life whether we realize it or not.