You have gotten some great advice. I am "friends" with my kids on myspace and facebook, and most of their friends are my "friends" too. I have told my teenagers, that it is my JOB as a mom to make the rules. They don't have to like it. I am only an a-hole when you make me be one.
Cell phone and computer use are only allowed if grades and other responsibilities are taken care of. If your grades drop or you don't keep up with your room, hand over the phone. Have her sign a contract about it. Be specific of what you expect.
On the other hand, if she has good grades, her room is clean and is being respectful to you and other house members she gets to keep her phone ALL night.
Kids need to realize that these things are privileges. We do NOT have to give them EVERYTHING just because everyone else has one. I call BS, not everyone has this stuff!! And another thing, I don't care if your dad gave it to you, if you are not holding up your end of the bargain, you lose it.
A big key with teens is to speak to them on their level. Sit down and say what you are feeling and why. I was called a DICTATOR. Hahahaha, I laughed, and agreed! You don't live in a democratic society until you are moved out and are paying your own way. As long as I pay the bills I make the rules. Oh and if I ask who you are speaking with or texting, you better answer me. That is not YOUR phone, you don't pay the bill, even if dad pays it, you have the right to know who they are talking to. At any time I will pick up their phones, if there is anything inappropriate, I delete it and take it away. I sound like a hard a&&, but I have only had to do this stuff ONE time. They got the message. My boys are 19 and 17 and my daughter is 12. We are very close, they tell me pretty much everything. But I ask alot of questions all the time. We pray together, we eat dinner together, we play board games, we hang out and laugh ALOT! My boys dont attend church with me any longer but my girl does. GOD is a very important factor in our lives.
This is getting long, but another good secret, your kids need to think that at any time you may just LOSE IT. Go whacko on them, scare the beejeezus out of em. I am short and have to look up to my boys, but they are never sure what I will do. Don't try me,you never know!! LOL, it is a joke around my house that I am crazy, but in the back of their minds, they really never know if I will go off or not. It works, trust me!!
Good Luck and GOd Bless!!!