Sticky situation. For your own sake, save every email from A and also record the times she called, duration of the call and such so that if she does decide to do anything, which she has no grounds to, you have backup and proof.
She sold the dog, at that point she gave up all rights to that dog. Look for B on the internet, dont contact her, just see if you can find out where she went to. Maybe pass along the information or something.