I had this same problem my place is not as big 5 acres and farmers and orange groves all around . I to carry a side arm but my husband said not to make a stink in the neighborhood as we are a small community so I went to harbor freaght and got a solar powered electric fence so far it's working out. I sat in my house by the window and watch them torture them selves for 2 hours the first day all with my scope and 17 right on them just in case.
You could also set a humane trap and haul them off to the pound. I would tell her that's where they are once she has to pay fines to get her dogs back she will find a way to keep them under control. Here it's $50 bucks to get your dog from the pound. Pam