Puppy wants to say hi to dogs but then cries/yelps once she does

Hi! I have a 6 month old puppy. She used to get very excited around other dogs and start sprinting around. Now when she sees a dog (mostly bigger dogs) she goes to say hi but then almost immediately yelps and cries like the other dog hurt her.

Is this just fear period? Or is there something else wrong.

Thanks 🙂