My DD is 16 and very smart, funny and although she has mood swings and ADHD, can be incredibly enjoyable to be around. However, she's had a problem with lying for as long as I can remember. I thought she would get over it, but she hasn't. Lately, her grades have been slipping and she lies about doing her homework and making up assignments even though she knows I can and will check with her teachers about it. I even give her warnings and she clams up. Yesterday, I told her I was going to email four of her teachers because her grades showed that she had no credit for some tests that she told me she made up a month ago and that if she had lied about doing them now was the time to either get them done or fess up. She said she hadn't lied and to go ahead and email. The first response came back that she did indeed lie about making up the test! I'm furious! I don't understand why she does this! She's being disrespectful to me and making me look like a fool when I email her teachers assuming it's their fault there isn't a grade, which is a horrible thing for her to do to me. I've tried everything I can think of to fix this. Taken away privileges (she lost her computer four months ago), told her no driver's license until her grades are fixed, taken away her phone, given her extra chores and even tried to set up a reward system instead. Nothing works. She continues to lie and not care about it. She continually makes bad choices. She sees a psychiatrist because she has mild bipolar disorder and her doctor feels that it could be her illness manifesting through making these bad choices, but I don't know if that's an excuse or what to do about it if it is. She is on medication, and is stable, so I just don't know.
Do any of you have advice on how to deal with a pathological lying teenager?