Okay, here's my two cents on this situation. :/ Tiffany was asking to be found out when she posted it in such a public place, but now she would like to pretend that she didn't want to be found out. Therefore, she needs a scapegoat to blame it on. I guess you ended up being the prime candidate. I hate to say it, but I think your friendship was over the first time she confronted you about this.
It's not worth feeling suicidal over, hun. I'm sorry that this is upsetting you so much, but I think it's something you'll just have to let go. You can't really repair it, when you didn't do anything (not really) in the first place.
I will say that quite frequently, in the middle and high school years, our friends begin to change and drift away from us. It's because in these years, our true personalities start to develop. Within time, you'll get friends who will be around for the rest of your life. It's hard right now, but just keep going. It will get better.
