Hello, it is not uncommon for yorkies to make that sound. It could be reverse sneezing or collapsing trachea. Or it could be just the way she barks.

Don't be like me and assume the worst. Gus does this once in a while and I used to worry but it is just reverse sneezing.
Here is a site that explains it better than I can.
http://www.angelfire.com/on2/yorkies/medical.html
Welcome to YT.