What treatment did your pup receive at the ER? Was she on an IV, or at least get sub q fluids? Hopefully she was also prescribed pain medication, as acute pancreatitis is very painful.
I would not worry about feeding her for now. Her pancreas needs to rest, and there is no point in feeding a vomiting dog. Continued vomiting causes more issues than not feeding and not vomiting. If she received fluids at the ER, she should be well hydrated for now. If not, and she can hold it down you might trying giving her just a couple of cc's of water by syringe every hour or so, only as long as she is able to hold it down.
By tomorrow morning if she is not still vomiting and hasn't for several hours, you can try feeding her a bit of over-boiled white potato or rice. Make a slurry with the water you boiled the potato in, to the consistency of a thick liquid. Try giving her just a teaspoon or two of the slurry to see if she can hold it down. If she hasn't vomited within an hour or two, you can try giving a little bit more but only tiny amounts at a time every hour or two for the next day or so. It can take weeks for a pup to get back to eating their regular diet about a serious bout of pancreatitis, and you will have to modify her diet to very low fat now that she has had pancreatitis.
It is very easy for a small dog to become dehydrated and that can be very dangerous. Especially if she did not receive fluids at the vet (and even if she did) watch for excessive vomiting or diarrhea, and head straight back to the ER if she shows signs of dehydration.
Dehydration in Dogs | petMD