I agree with debbie, this is a form of tantrum (albeit silent) and she is testing you. She is ignoring you so I would suggest you do the same to her, carry on playing, talking, walking, (whatever you were doing) and DO NOT try and cajole her out of it, it will not be long before she realises no one is interested and that only she is missing out! When she does eventually come out of it, do not say anything to her and carry on as if nothing had happened. Good luck