May be it is due to personal health problems that they cant go into on an advert. If its k.c. reg it will have all its paperwork for you to see, aslo vet checkups, innoculations updates, should be there for you to see aswell, You could ask what the mother and fathers name is and then check up with the kennel club. If not there is nothing you can do but listen to what she is saying, it is up to you if you believe her or not, but dont just get it because you may feel sorry for it. It may be snappy with little kids but good with older ones, It is hard to tell, and I dont know what to say to help you. If you know where abouts the dog is from, you may be lucky enough to see a neighbour and drop a few hints they may be able to tell you something. thats a long shot though. Hope you work it out and it goes well. xxxx