We went for a walk in the woods and Winnie was on her leash. As we entered the woods, a big, muscular pit type of dog was on his way out. I had Winnie about 4 or 5 metres away from this dog. Winnie stopped to look at the dog for a few seconds and the other dog looked over at her and I thought that was the end of that and was going to continue walking on. All of a sudden this dog lunged straight for Winnie and was snarling and barking and growling. He was so strong, his owner had to use all his strength to hold him back. Of course this spooked Winnie and she jumped back. The dog left with his owner dragging him away but he was still snarling and growling. Winnie started whining like she was crying. We gave Winnie a bit of comfort and she stopped whining and carried on walking and seemed happy sniffing everything and looking at the birds and squirrels. We came across other dogs but they were all in the distance until we walked down a path and another dog (a collie type) was lying down on the path (also on a lead) while his owner was chatting to someone. Winnie would not walk past the dog. She was staring at this dog lying on ground but would not walk past it. I stood between her and the dog as I could hear Winnie growling, then she lunged towards the dog and was snarling and growling at it just like the other dog had done to her. She has met so many dogs in the woods and normally they are friendly and sniff each other and act playfully but this was the first time she has been spooked by another dog. What should I do to ensure this doesn't become a problem? She is not an aggressive dog so her reaction to the second dog must have had something to do with her being scared by the first dog.