Help! With b!tchy daughter?

My 16 year old daughter has been really b!tchy recently.She has been nagging me ever since last christmas to buy her some new low rise skinny jeans. So I was thrift shopping the other day and I scored on a pair of low rise dark wash skinny jeans in her size, only look like they had been worn a couple times, but she said 'ew' and refused to wear them. I also found porn on the internet history of her laptop, and even porn videos downloaded onto it! She also smokes pot with her hooligan friends on the stairs to my apartment when I'm not home! My other daughter, who's 5 told me that she had been blowing smoke into her face to give her a contact high! 3 months ago, I found LSD hidden in the back of her ps2 in her room! She also just got off probation last summer. AND last weekend she puked all over our living room couch, because she was wasted. I know that some of her friends do meth, so I am worried for her. What should I do about her?