
What does she look like - are her hackles (the hair on her shoulders) sticking up, is she showing teeth, are her ears back, etc? These sort of things will give an indication of how she's feeling, whether it's playful or fearful, or if she's just not sure. As an example - my bitch and my brother's bitch both have mad moments on leash; depending on the situation, both throw themselves at the end of the lead, leaping around, very vocal and so on. My bitch does it out of sheer joy at seeing one of her several "boyfriends" - her tail goes ten-to-the-dozen, hackels down, ears held back (can be a happy as well as aggressive/fearful sign), bouncing around and making high-pitched yelpy-wimpery noises. My brother's bitch does it at basically any dog when she's on leash, and it's out of fear (being trapped on a leash) - her hackles are up, ears pricked (as much as greyhound-type folded ears can be!!), sometimes she shows teeth, her tail wags slowly, she also throws herself toward the other dog, and she makes an awful baying sound. Same type of action, but different basis, and it's evident from her body language and vocalisations.