K earlier I made a BS post because I was too lazy to think of something decent so here's a post for the sake of karma.
Multiple factors always contribute to suicide. There's no chance one random altercation is going to push someone over the edge. Her life may have been filled with the typical anti-social assholes who only want to make other peoples' lives hell because THEIR lives are hell. This bullying along with the self hatred nearly everyone goes through in puberty alone could give one suicidal thoughts. Not everyone's going to over the edge with little things like that though. My guess is she was having an awful day to begin with ultimately leading to her banning from Facebook. She could have taken the ban several ways, such as her parents no longer loving her.
But my point isn't just finding excuses which may not even exist. My point is there's no chance Facebook was the reason for this suicide. Bringing me back to the point of "her parents might not love her anymore..." she may have been trying to explain to her parents how something went wrong or how someone put the blame on her and she didn't do it er whatever.
She may have been afraid to talk to her parents too. She might have feared things would have gotten worse if she did talk about what was troubling her. I'm going to use that idea to lead my next points into why she committed suicide.
She was afraid to talk to her parents and never did. Her parents found out and punished her by taking away her Facebook. She might have tried to persuade her parents to look at her side of the story and failing to... or she still didn't say anything. I'm going with the latter because of her suicide note. She blames it on her banning from Facebook, which is a ludicrous idea in itself. I believe that she was too afraid to give her true feelings even though she was well aware her life was going to end.
My most educated guess (and this is coming from some kid in North Dakota) is that she was too afraid to talk about her problems, so she took her life so she never would have to, keeping it forever in secret with that ridiculous suicide note.
There. a well thought out post. I'm going to hide under my blankets so I don't have to answer responses.