why all of a sudden she stopped chatting with me? we were chatting on facebook and all of a sudden?

[The]

She stopped chatting with you via Facebook because that's not actually chatting, it's typing. If you want to know what happened the only one who will ever really know is her. And the only way to truly find out is to...
**ASK HER YOURSELF!!**
And NOT on Facebook, not via text message, not through a note with the two check boxes "If you like me, check the 'yes' box, if not check 'no.'" ....not through a friend, Twitter, or whatever else you're into...
FACE TO FREAKING FACE!!
Why? Because maybe she didn't want to have an on-line relationship and wants to be with you, but you will never know unless you ask her yourself.
And if she doesn't like you, then that sucks, I know, but at least you will know too, and then you can move on with your life.