Do you use a collar when you walk her? Small dogs often have a very sensitive trachea, and during or after walking them they may make a coughing sound. My toy poodle mix, Molli, will make coughing and 'reverse sneeze' noises throughout the day and they're usually associated with stress or excitement. Do bring it up to your vet. From my understanding, Kennel Cough usually has a constant coughing noise.

Congrats on the new addition to your family! She is absolutely adorable!