Hello.
Sorry, but I read your first post wrongly as your dog only had issues off lead.
She is still young and a big dog probably looks very scary to an 8 pounder
As I said before, it could be that she just can't deal with big dogs and has to be kept away from them.
My previous dog, only five pounds, hated ALL oher dogs and I just had to steer clear to prevent a war, LOL! They all have their issues!
As for fleas etc, it is good that most dogs you meet are treated monthly, and we all take risks when walking our dogs in public parks and places. I don't know if you have them, but we have closed areas specially for dogs only and we call them specifically DOG parks where the dogs are usually off lead and able to play unrestrained.
These are not very big and can get very dirty if not well maintained, and if owners do not pick up after their dogs. That is why some people don't risk taking their dogs there. General use parks tend to be larger, but still can have risks, but we take them or the dogs would never get to walk!
I am sorry you had this scary experience recently so that you had to pick up your baby, but I guess you just have to give the biggies a wide berth.
Hope she gets better as she gets older and is not so scared, and that she has enough smaller dogs to play with.