So i told a girl yesterday ive liked her for a while, the next day she went around telling EVERYONEE about this, at least 40 people at school now know. its not that im shy about it im just wondering why she would do it. we are both 16...why would she do something like this? is it to test if im serious or is she just an attention seeking bitch? girls please...help?

Did she tell you she liked you back, if yes, then she's probably just proud that you two will probably be a couple soon, so take it as a complement, is she doesnt like you in return, she is being an attention whoring bitch who wants everyone to 'look at me, someone likes me'. Hope for your sake it's the first one.

She's either claiming you... or being an attention whoring bitch.

If you want to find out, start a rumor that it's not true. See if she gets pissed or sad.

Yeah, it's either to "claim you", or ruin you because she needs to feel good about herself, and you happen to be a particularly unassuming target.
Nobody knows until you ask her on a date. Although, I suspect the latter.