
If I were you, hard though it would be, I would not buy this puppy. She clearly has problems, that may well be lifelong. You deserve to have a healthy puppy to share your life with, not one that's going to be a worry and possibly a financial burden in vet fees for a long time to come.
We will need more information to help you find out whether this person is reputable, it may be that you need to conduct your investigation off forum or at least by private message.
Dawn R.