Does she have fever? Is she sleeping at night? Is she eating breakfest? Just a few questions to start..
There are many thing that could be wrong. There are a few questions that need to be answered before anyone can make a judgement about this, such as...has she ever done this before? Did she sleep well the night before, or has her sleep rhythym been disrupted? Does she have allergies that would cause this? The point I am trying to make is that the only one who can make a diagnosis is a doctor. I suggest that if this happens again (I am assuming this is the first time), see her pediatrician immediatly. Sorry, but that is the best I have to offer you.