fibricator

A person who lies, usually small lies. Someone who manufactures lies in a believable way.

Johnny won't stay out of his sister's room so:

Sister: Mom Johnny stole my diary! (lie, fibrication)

Mom: Johnny come here right now! (a proper thrashing ensues).

Later-

Johnny to sister: Your such a fibricator. (That night Johnny does steal the diary, and passes out pages at school. Mom then finds out through facebook that her daughter's a whore.)