I think you're going to have to give more information about the type of guard dog training your dog has had. At this point, I believe what you're doing is the only thing that will help her figure out that she doesn't have the same job that she used to anymore but it might take quite a bit of time. You are pretty much going to have to start correcting her for doing what she is used to...barking and protecting property. She has to re-learn that this type of behavior is wrong and depending on the training she's had, it might be extremely difficult.
But please provide more information on the type of guard dog she was and what exactly she was expected to do.
CD RE TC HIC 7/10