Welcome. You have found a great place to call home with some fantastic, knowledgeable people. You need time and patience to overcome all that she has been through prior to you getting her. Unfortunately, a lot of times when we get rescued dogs, although we may know where they came from immediately prior to us, we don't know their entire history. Regardless of what went on before, you can retrain a dog and work through their issues. We have had Cody for a year and we are still seeing changes in his personality. It can take an abused dog 10 - 12 months to truly accept that they are safe and are home and can be themselves. For a Pyr, that means guarding. For your Pyr, that means "I have a great home, with people I love and I am going to guard you so well, you will never want me to go away." She truly does not understand uninvited people just walking into her second home. She spend the day with you at work, so it is her daytime home. She feels that she needs to protect it. See if you can come up with a word to say each time someone comes in to the store or your home, like "friend". She is smart enough to associate the word with the action. If you say the word each time and utilize some of the tips above, treats, walking a person in, etc. she should quickly learn that the word means it's okay. If you don't say the word, she is entitled to bark. That way she is still guarding and can be trusted to protect you. You are doing a great job with her and she will come around. Just give her time and keep up the good work.
Kathy
