To dream that you are lying to someone about something, means that you are hiding some secrets. On the other way, you think that others are invading in your privacy too much, therefore you are protecting yourself by lying. If someone else lies to you, you shouldnt trust this person in your waking life either. The lies could also mean that you should give more privacy and freedom to this particular person.
Read more about dreaming of Lie in other dream meanings interpretations.