Good Morning and welcome! I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
This is not unusual for those dogs that are territorial.
AS you are aware. this is a very serious situation. the first thing to do is to have your vet examine your girl since this may be due to a medical condition especially if she is not spayed. Other metabolic problems can cause this aggressive behavior that can be treated with medication.
If this is ruled out, then I strongly recommend that you seek the aid of a veterinary behaviorist which you can find using this LINK
I only say this because now, you will not be able to trust your girl until she has calmed down. There are calming agents such as a DAP Collar that decreases anxiety of this is causing this aggression or Rescue Remedy that also decreases anxiety. Both can be purchased at the pet store.
Your vet has medication that can help you train your girl out of this aggression by establishing yourself as the "Alpha Dog" and obedience training so she obeys you when you say NO!
You do have options and after speaking to your vet, they will be able to direct you so that your girl stops this bad behavior.
Does that make sense to you?
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please REPLY so I can clarify for you.
Sincerely, ***** *****