Millie had a run in with a dog once, it was a rather over zealous collie dog (one like lassie). The owner couldn't control it. There was also two young beagles.
Millie was playing with the two beagles and having great fun when the collie joined in. She was too big and boisterous, but not dangerous.
Then as we all parted and went on our way, I called Millie to 'come', she looked up and started running to me with much delight and focus on me. The collie came charging over wanting to play some more and ran her over. Millie gave such a crying yelp. Instinctively I scooped her up to check her over. The owner of the collie was very apologetic and was worried she'd been hurt. I think all she had was a big fright and perhaps a bruise.
I was concerned that this would make her nervous around dogs, which I really don't want. But luckily the two beagles came running back and were looking up at Millie with such concern as if to say 'whats happened to our friend' (it was just like a school playground,

). I promptly put Millie back on the ground inbetween the two beagles. She was fine and sociable straight away.
Millie has a tendency to greet the owner of the other dog too and when play or interaction gets a little rough for her, she hides between their legs as if to say, save me from your dog!.
What I'm saying is, you'll soon learn what your puppy to happy doing and what other dogs are like. It is a little nerve racking, but trust your instinct. If you don't like another dog or owner, take a detour, put her back on the lead etc.
