There are many people that just cant stop lying. In order to avoid the truth this path is chosen. A lie that is said for someones benefit is to cheat another. However there are some people that always lie, meaning that they are looked upon as liars for everything and anything that they might say. Anyone who has the habit of lying continuously is called as compulsive liar. It is a condition where a person is just unable to speak the truth, even if he tries to put it in a simple and truthful way there happens to be a point at which he will be unable to continue with the harsh truths and in order to avoid this he will start it all again with lying.
Compulsive lying is also like an addiction just like sex, drugs, smoking and so on. Just as a person requires help under all these conditions, the situation is the same even with compulsive lying. Any person can be a compulsive liar; your daughters, sons, husbands, wifes, girlfriends, boyfriends etc. Instead of avoiding your compulsive liar (friend or spouse) you can help them deal with this disease just like you would do in case of a more evident addiction.
For this you dont have to directly approach them and tell them...