1) File a police report against her for harassment and cyberstalking, possibly even extortion (making threats to make you give her money)--making threats or taking actions to intimidate, scare, etc. you are not legal.2) If you did not provide a puppy warranty or guaranty, you'd only potentially be liable if you did know of the illness but misrepresented (lied about) it, since that could constitute fraud. If she were to sue you (and unfortunately, you can't keep her from filing a lawsuit if she is determined to; the courts do not "prescreen" lawsuits to see if they are valid), to win, she would need to prove in court by a "preponderance of the evidence" (that it is "more likely than not") that you knew, or logically *must* have known, of the illness, which may be very difficult for her.