I see a couple things that are good
1. They only breed yorkies
2. They make an appt at their home to pick up the pup, this is where you can see the mother and father.
4. They have a full year health guarantee
3. They do not ship their pups
I see a couple things you may want to question
1. You are locked into a puppy once you make a deposit. The $300 is transferrable but not refundable. In other words you can get another of their pups with the same deposit if the one you wanted was not what you wanted, but you cannot get your deposit back.
2. The site says the weight and size of the male but not of the females. Its clear she breeds small yorkies, however she does not use the words teacup or toy or anything so that is good. I'd ask the size/weight of the females. You want to make sure she is breeding within standard yorkshire terrier size which is 3 - 7lbs. Too small and you could end up with a baby that has health problems.
I think that covers it. Overall she looks decent judging by her website, but we'll see what others think.
Good Luck!
Welcome to YT by the way!!!