As Larry said, usually it's the infection that's causing the spike in BGs. I wouldn't worry too much just yet about it. How high are they soaring and how long does the vet think it will take for the infection to clear her system? You might want to give a token amount of insulin for a little while to counteract the hyperglycemia being caused from the infection, but it might not be necessary if her numbers start to come back down relatively fast or they aren't going up too high.