We generally go by treat the child not the fever. Personally I'm wary of fast rising fevers but usually it goes up and settles at a certain temp. Seems to be 38.8 in this house! If they go over 39 that's when they get miserable, dd1 gets headaches and DS tends to throw up. So that's when we start treating the child. I also don't like that panadol/nurofen makes them feel well enough to get up and play etc. when they need to be resting.
I hope she's feeling better soon.