jealous border collie

Question
My family consisting of four children all teenagers and we have been caring for a dog part to full time for a year now for an elderly man. The dog is Australian shepherd and pit bull, two years old. She has a very humble and sweet tempermant. Her owner recently passed away so we have transitioned her slowly over to our home. She LOVES it!
However the previous owners, daughter, who comes to visit on occasion brings her border collie and this dog is MEAN to our dog. But I can't say or do anything because our dog is not been legally handed over to us yet. The owner's daughter always makes excuses and says that her dog is just trying to get my dog to play. Well, biting, growling and jumping on her to control her does NOT look like playing to me. She is jealous and trying to teach our dog to be submissive and the the thing that bothers me the most.....this isn't even the owner's daughter's dog's property. She just visits. What do I do to protect my dog without upsetting the "Know-it-all" daughter?

Answer
I am not an attorney but I offer the following advice based upon experience in my state.  Take your (inherited by default) dog to the veterinarian.  This will establish a legal ownership.  I don't know what state you live in but in most states this dog would be considered "abandoned" by its owner (even though deceased) AND this woman has made NO DEMAND for this dog, thereby apparently acquiescing to your ownership.  By establishing "ownership" yourself (paying for veterinary services) you create a perimeter that the deceased owner's daughter can really only penetrate in court and that would involve either small claims or hiring an attorney.  NO attorney is going to take on such a case unless this woman is foolishly willing to pay thousands.  In small claims court, the dog is in YOUR custody, you have established ownership (veterinary record) and it's highly unlikely any magistrate would (or could) force you to hand over this dog.

This is YOUR HOUSE, that dog is in YOUR HOUSE, this woman is not welcome (nor is her dog) into YOUR HOUSE without your willing participation.  As the house owner (or lease holder) you are in your legal right to tell this woman that she and her dog are not welcome in YOUR HOUSE.  Do NOT let her in, no matter how long she "rings the bell".  Try to avoid escalation by explaining to her that HER dog's behavior is WORRISOME to you, that you have teenagers in your home and that her dog's aggression toward the dog her father left WITH YOU is causing emotional problems with your kids.  The former owner's daughter has NO LEGAL RIGHT to be IN YOUR HOME unless YOU ALLOW IT.