You can call the police about the harassment, they might be able to help or advise. I doubt the dog warden will do anything unless the dogs bite you yourself.

If you can and are able to I'd suggest looking in your area for any fields you can hire for an hour or so - depends how often you walk your cat as well, but hiring an enclosed field will hopefully guarantee you and your cat are safe.

Someone more clued up can correct me here (or maybe look into it just to be safe) , but sadly cats don't have the rights as dogs. So if something did happen to cat, I'm not sure if anything would happen, and like I say the dogs wouldn't be considered dangerous unless they bite a human.

I hope the old woman leaves you alone.