This brought back loooooottttsss of memories!!!

Firstly, you should treat people how you want to be treated. This doesn't mean that you should let them use you though. Think of the quote as a sort of guidance to making new friends or when you have to make a tough decision, like the facebook hacking. If you knew the person, were friends with her, and joked around a lot, then you hacking her profile could have been interpreted as a joke (I know a lot of my friends share their passwords, and tend to write something on each others pages as a joke; nothing mean though). But seeing as you didn't know her, you should have thought it through. You should have thought, "would I like it if some random girl in my school hacked into MY facebook page?".

Secondly, don't beat yourself up about it. You're still at the age where you're easily influenced and don't think through things properly. It's the same for anyone at your age. I know I did a lot of things which I didn't think through, or now that I look back at it, were done for stupid reasons. People get over it, just give it some time (i'm great friends with a girl who used to be my enemy in primary; we both admitted that what we did to each other was stupid).

Thirdly, contrary to popular belief, not everyone loves the popular girl. There will be people who dislike her, as, after all, you're simply human, and not everyone can like you. I don't know what exactly you wrote on her facebook page, but it couldn't have possibly been that bad. There will be a few people who don't mind, not EVERYONE will hate you, and not everyone is perfect. There will be others who have done something they deem as bad, so they can't exactly judge you.

And lastly, people are free to make friends with whoever they like. Telling someone that they can't be friends with someone, will only make them hate you. Like I said before, (in your previous question), ditch Emma. She is only using you, especially now, because she is afraid of being alone. Let her know that she can't use you, that she can't keep coming back to you whenever she doesn't have anyone else; give her a taste of her own medicine. Try to make friends with someone else, and don't let people take control of you. If you don't want to do something, then don't. If they are your friend, then they will respect your decision. If you let people do what they want to you, then they will only make fun of you for not being able to stand up for yourself. Don't forget, that the reason you go to school is to learn, not to make friends. You have millions of chances to make friends, the kids at your school aren't the only people in the world. You could make friends outside of school, and don't forget the ones you already have (like Chloe for example). If you want a fresh new start, then you could always try going to a different school. You don't have to take my advice, you don't even have to read this, but this is just what I would do in your position. Hope it helps