Civil

The question you imply is whether the legal position staked out by your father's girlfriend has any legal merit. It does not. Dogs are personal property. She has stolen your personal property by refusing to return your dog. You can file a complaint with your local authorities. You could sue in small claims court (assuming this is not an AKC champion, which might open up jurisdiction for the district courts). Or you could prevail upon her and your father's common sense. Life is too short to steal a child's dog.

You might owe the veterinarian's bill if the services were necessary. Or you could sue for "fixing" your dog, which may or may not have been necessary. And if the dog was one that had marketable stud services, that would be another basis for money damages.

Good luck.