So sorry to hear your story. I would think, taking everything else into consideration, the pedigree is probably a fake - or it may be real but for another cat.
May's advice is probably the best avenue you have to explore this further. Let us hope the vet's certificate is genuine but then they may not be allowed to divulge the lady's information. Is it possible you can phone the newspaper where you saw the ad and see if they can provide any info - they must have some details as presumably she would have paid for the ad by card. If nothing else you could complain to them about her and hopefully they may not place any future ads for her.
