If there is vomitting with the diahorreaha (sp?) and the high temp I would be taking her to her hospital or a 24hr clinic. More to ease your mind and they are likely to make her a priority given her age and symptoms.
If you can't get to one, ring Nurse on Call 1300 60 60 24 and see what they have to say, even ring the after hours medical care 03 9429 5677 and see if a Dr can come to you. It doesn't sound like AB's are going to work as it does sound viral.
I would be keeping her with you all night and try and get some fluids into her. Keep up with the panadol.
I hope your little girl it better soon BC