Thank you all for your responses! I went to the vet just to make sure she didn't have a cold or anything and told him when it happened. Chloey got a perfect health bill and he said it was something Yorkies were prone to do! He also suggested it might be reverse sneezing but since she wasn't doing it when we were there (obviously

) he couldn't give me any real diagnostic. Just said there was nothing to be worried about.
Phew! I was terrified of it being trachea problems