My dd went through this despite growing up with a dog. She was never scared of our dog but would gp to pieces near any others. It was a long, slow process to help her get over it. We started by letting her see her siblings gently interact with small, old dogs who were held firmly in their owners arms. From there we went to staffies like our dog as she felt safer around them. Then onto other dogs. Every interaction was controlled, brief, a d with lots of positive encouragement. If she wouldn't pat the dog then her siblings and I still did to demonstrate that there was no reason to fear. She still doesn't love dogs, especially very large ones, but she no longer runs screaming which is a huge improvement.