I know this breeder, Let's Talk Yorkie, to be very reputable.
To those complaining about the guarantee, you need to come to grips with the fact we can't guarantee everything AND keep prices where you want them. Being "reputable" means we've demonstrated over time that we care deeply about our breeding and step up and work with you when things go wrong.
By the way, I think she's saying to have the puppy checked by a vet withing 48 hours for an initial wellness check, and further to notify within 48 hours of diagnosis should a serious life threatening congenital/genetic defect appear. This is where reputation plays a role. Interview the breeder about just what all that means.