Not a hiss but its my cats hiss?

Earlier today we had our friend come over and they brought there dog. Well my cats never really been good at meowing I had to work with it and she can but chooses not to meow. But she purs constantly even when I have bathed her once. She doesnt stop purring and its nice. Shes always happy. Well the dog came in and she puffed up like cats do went under the couch the dog went to go sniff and instead of a hiss it was like a loud exhale like phoof sound like a puff of air, now i know it isnt totally normal but have you ever had a cat not able to hiss right or meow good enough? Is it rare?