They will overstate a point so much that lying will be necessary. They can't handle insensitivity either, therefore it's unexpected that they'll lie to cover up their offensive words. Their transgressions are really worrying.
They rely on lies to attract more attention or to make themselves the centre of attention.
Even if they are egotistic and don't want to lie, they will try to appear more superior by making up lies about their success, popularity, etc. They won't look at you directly since lying prevents eye contact.
Because it's so simple for Geminis, they can modify the reality in the span of a single blink of an eye.
They must maintain their position as the group's "most social person," thus they avoid conflict at all costs. They cannot have a negative reputation, and they cannot have the label of "lie" hanging over their heads.
Because they are skilled at lying, they do it. They have an impossibly kept veneer that is impossible to recognise.
They continuously make up stories about anything and everything, and they always get away with it. By concentrating on the intricate, multi-layered stories they fabricate, one can spot their lies.
Although Libras dislike lying, they will do so to protect themselves. They stay away from conflicts because they find them to be awkward and uneasy.
To avoid getting into problems, they will slightly distort the truth. They will suffer significant losses as a result of their lies as they eventually lose their balance.