My granddaughter is 6 years old and she lies. Is this just a phase or a preview of things to come? Is she just seeking attention?
Whether it is just a phase or a habit she is forming, her lying needs to be addressed as a negative behavior so she will learn that it is not acceptable. You and her parents need to stop this behavior from happening just as you would any other negative behavior.
Address it immediately when you see it happening by describing specifically what she is doing. Then issue a consequence for her engaging in this behavior. Follow up by teaching her an alternative, more acceptable behavior that you would like to see instead.