Nobody at that age is really depressed... I hate to say it like that, but... I mean I understand having stress and stuff like that, because yeah, its hard to be 13, but depression? No.
There's nothing to actually be depressed about unless some majorly tragic event happened, and in this case, it doesnt really seem like anything "bad" was happening to her except somebody was pushing her buttons over the Internet... so basically she was just stupid. I wish people would stop using depression for everything when they're freakin teenagers.
Its very easy to be depressed at a young age. And how do you know that nothing major was going on in her life?