My boys both stopped napping at around that age. It is hugely frustrating, but normal. And it's just going to be tough for a few weeks as she adjusts.
One thing that helped is having "quiet time" in the afternoon, about the time when she used to nap. With my first, he had to stay on his bed and could look at as many books as he wanted. There were stacks and stacks of books on his bed! At first, he'd fall asleep half the time, and he'd get his nap that way. But he gradually fell asleep less and less often, but he still had to stay on his bed for a whole hour.
He was my compliant kid, though. My second one, not so much. Especially because his big brother was up and playing, he wasn't aobut to stay in his bed! He's not one to look at books for hours on end, either. So we had a movie in the afternoon where my boys could sort of veg and relax for a while. I needed it, and they certainly did, too. It made dinner time so much less dramatic. Less crying, less whining about our food, less refusing to eat, etc.