Hi, and congratulations. Did Hillsborough county animal services say how they 'know' she is full blooded Yorkie, by any chance? Just curious, of course.
Regardless whether she is purebred Yorkie or not, she is adorable and you are wonderful for giving her a home. I believe she will be only too happy to reciprocate fully. If you do the DNA test, it would be great if you post the results.
Welcome to YT, I hope you enjoy it here.