Welcome to the Dog Forum.
First, I would strongly suggest that you carefully study the resources in this thread and share them with the child's parent: https://www.dogforum.com/general-dog...s-dogs-115969/
Based on what you have written, a dog bite is imminent, which of course means that the child will be scarred and Animal Control will take and euthanize your dog. If the child is too young to understand that she can't keep following the dog, you need to physically separate the child from the dog at all times, as in closed doors and physical barriers.
Your dog is throwing out ALL KINDS of warning signals that she's fed up with the child and about to bite. That doesn't mean that you've got an aggressive dog. It means that the dog's patience has been sorely tested.
I have the most gentle, most easy-going dog that you can imagine. But, he's now a senior. He's become blind, hard-of-hearing, and arthritic. About half a year ago, the small child of a friend tried to pet him. My dog started to move forward, and the child followed and continued to try to pet him. My dog turned and snapped at the child. The whole incident took less than two minutes. The child was not doing anything "wrong," but I think he just hit a sore spot. That's the last time I've ever let a child approach my dog.
Again, carefully study the videos and articles in that thread. You're right. A bite is going to happen. You and the child's parent have to do everything you can to prevent it.