Hi
I would get her spayed end of story. the vet would not be allowed to tell them why because of confidentiality. you should never be made to produce more puppies there are too many as it is and border collies get such a raw deal. it sounds to me like theses people are just using you. if you saw other relatives could this be a puppy farm I wonder? hope all goes well for you do the right thing by your dog you're all she's got.