You are correct, resource guarding is a tough thing to work on especially when the dog guards so many different items. You may never fix it, but you can certainly manage the dog and contain her in a safe space like an ex-pen when you can't manage her. Our management video may give you some ideas that are helpful.
With a dog like this, I would manage her every move and teach her a command such as Leave It or Yuck that means "whatever you have is now off limits". Many dogs have guarding tendencies; they just vary in intensity.
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