OK, I'm sorry, but I do not allow growling of any type towards any animal or myself or guests at my house. To be totally honest with you, I'm not sure why she's growling or what it's called (resource guarding), but it would not be tolerated. Sara, it sounds as if you are taking all the right steps. She has to be taught that growling will not be tolerated. I know, by reading, that feeding time is no longer an issue. When I first brought Scout home at 10 weeks she was eating and one of the cats casually walked by, he wasn't looking at her food and she growled at him. I was sort of shocked. So I corrected her by picking up her food and telling her No. This stopped. All four of my animals eat right next to each other. Of course I am there to supervise. Scout finishes first then she goes over to Breeze, who ignores her, when she finished Scout jusmps up to her dish. She eats on an elevated dish. Then seeing there's nothing left (are you kidding!) she tries to get the cats food and I have to correct her.
As far as treats go, my two only get treats at night before they go to bed. I know it's a little different for me because my other do is a newf and much larger, but Scout will try and take the food from her mouth. I have also had to monitor this. Now at bedtime I feed them treats at the same time. Scout on the bed and Breeze on the floor. I do have to watch carefully. I think this would be the only time Breeze would be cross with Scout and possible give her the warning that she deserved.
Just like any other training consistency is the key. You are an experienced dog owner you know all about that I'm sure.
I've had a dog in my life since I was 5-6 years old. We never had a dog growl at us at anytime, for any reason.
Sharon, proud Mom of Scout (tri) and Breeze (Newfie)