I think on average yorkies are just as healthy as other purebreds....each seem to have breed specific medical problems to be aware of. Because of their small size they do seem to get into dangerous situations more so, than other larger breeds.
Honestly, I never worried at first when I got Ruby....not until I had been on YT for a few weeks and reading, did I even start worrying about things - like you!
Unless your Scarlet is exhibiting symptoms of illness (did you have anything specific you're worried about?) I would stop worrying and enjoy her.