Quote From: romac101 I'm the mother of a 12 year old girl. And quickly reaching my wits end. She lies to her dad and I on an almost constant basis. We are starting to think if her lips are moving.....it's a lie. Sneaking food or hiding food, report cards and hiding dirty laundry are an ongoing thing. I"ve gone to the extent of making them ( we have 2 kids, one boy) sit at the table and eat what ever they got caught sneaking till they were almost green. It worked. The laundry, I took all her clothes away and left her with only the basics to get through the week. I did that for 3 weeks. It seems to be working so far. 
Report card time, after asking if I was in for any nasty surprises and assured no everything is fine....I was shown a terrible report card. I sit with the kids as they do homework, help if they need it and ask if stuff has been handed in. They have agendas that assignments are written in, I check them and go through them with her. 
We have tried talking to her, we've grounded her, we've taken priveleges away. I've read Dr. phil's advice columns, today her room is getting stripped to the bare minimum. And she will be spending a lot more time there. 
My biggest question is this: if this doesn't work, what do we do next? And there is no way she could be the only kid doing tis stuff.....other parents must just not admit to any of it. 
Personaly, I'd stop after you took most of my clothes away. lol. I'd suggest not letting her do anything. That would make anyone stop. No tv. No phone. No computer. No friends. Nothing but school, homework, chores, showers, and bedtime. Anyone would stop if it became that bad.
My mom's a strict but loving, Southern woman. I was taught that if you lie, everything is taken away. Lying is wrong. I've learned that. Apparently, your daughter isn't scared that you'll punish her. Which it seems like you've been doing. But if she lies about where she is, check up on her. Call the house, call the place, stay with her at the mall. Don't be incredibally clingy but stay in the mall with her. Like if she's in a store stay outside the store and don't move until she comes out. Take all fun out of her life if she lies again and maybe she'll learn.
This proves how my mom is, Maybe it will help.
My sister was supposed to be at a friend's house, sleeping over. At two o'clock in the morning my mother called up the house to ask if Christy, my sister, was there. The answer. No. My mother, becoming incrdibally mad at this point waited until my sister was home the next morning to break the news. You lied, you get punished. No anything.
If she lies punish her. No matter if it's the tinist of lies. Punish her. Apparently it's the only that will work at this point since the point hasn't gotten across to her yet. Good luck and I hope it helped.