Let me first say that I feel sorry for everything that your family is going through. This has to be a very tough situation. Did you see it coming or see any signs of this kind of behavior? I have a 12 year old son, so I know some of what you are going through. He's a good boy, but I have to help him choose his friends because he thinks everyone is good and unfortunately, that's not the case. He learned after one of his "friends" stole his IPOD.
Now a few suggesstions and my own opinion on kids with cell phones, internet access and too much communication with other kids that have nothing better to do.
Make sure your daughter is involved in some afterschool activities. You didn't mention any in your request. Keeping children busy with sports, music, art etc., will help to eliminate their bordem and their need to be on the phone all evening.
Family dinners should always be with everyone in the house....if everyone is at home. Don't give her an option. We tend to give children too many options these days. These are the times that you can talk to children about their day and offer loving suggesstions and comforting words as well as praise for the good that they are doing.
I don't think Myspace or any social networks online are beneficial to children. They can get into too much trouble and they have far too much freedom it seems.
Texting is "dummying down" our society. As well as not allowing children to learn good communication skills. Children need to learn to communicate with their eyes, with a pencil and paper and with their mouths. What happens on her first job interview?
Don't allow her to make the rules. She's way out of control. You're going to have to have a long hearfelt talk about who the parents are in your household.
I am pretty old school and if my child exhibited that type of behavior, I would take EVERYTHING from her. Including her bedroom door...yes, take the door off the hinges. She has to learn that being in your home is a privilege. She needs to follow the rules and behave like a young lady before she gets anything back. I wouldn't allow her internet access at all without your supervision. Place the computer in the family room so she can't sneak and do what she wants.
I would also go to her school and find out why the children aren't being properly supervised? How does she get away to go "make-out" with a boy?
Also, as her parents you have every right to judge her friend and advise her on who she is allowed to associate with. You didn't give birth to her and raise her just to have someone else take over and instill their values upon her. Yes, make sure you know the parents of all of her friends. That's not just your right, but your JOB as her parent. You have to protect her in every way you can.
Be hard and strong. Tough love works!!!