I too could have written this but dd is 12!!
She has consequences when she gets caught lying, but even then she vehemently denies lying even when the evidence is clearly NOT in her favor.
I told her that her "AIM" in the situation is normal and healthy, but the way she is going about it is not appropriate.
The problem we have with consequences is, nothing seems to have an effect. We have taken away electronics, phone, sleep overs, school socials, etc. Short of bread and water and a bare mattress on the floor...and nothing seems to get the point across.
