I totally agree with everyone. She gets out of the hassle of owning/caring for the stud dog, but having him at her disposal whenever she wants.
I wonder what you paid for him. If you neutered him and were sued, what would worse case scenario be? It would be small claims court and I don't think the judge would make you responsible for anything more than the cost of the dog.
I have a dog who was never bred, was neutered and still marks and it is awful!
I would never chose to have a stud dog as a pet. Good luck.