on 01-06-2013 10:39 AM
Without taking her to a veterinarian it's impossible to diagnose the cause.
Just like people, there are a vast array of reasons why she may be vomiting. It could be anything from a virus, to poisoning, or stress. The severity of the illness will depend on how frequently she's vomiting as well as other factors like is she lethargic? Is she shaking or acting out of the ordinary at all? Is she able to keep anything down?
I'm not a medical professional but if she's just vomited once or twice and is otherwise acting normal, eating and drinking, playing etc it's probably safe to say that she just had a tummy ache and should rebound. If however, your suspect that her vomit looks suspicious of poisoning or her behavior is indicative of a serious virus or other ailment definitely get her to a vet asap.
I hope that helps!