Behavior Advice and Next Steps Advice Requested

My wife and I have a 6 year old female GSD, along with two young sons, (5 y.o and 1 y.o). Our GSD was trained extensively by a professional trainer and is VERY well trained in the traditional sense. Since we have gotten her as a puppy, she has been very reactive to other dogs, what I could classify as extreme resource guarding. Through years bad experiences with other dogs, we have completely removed any interaction with other dogs, no dog parks, no family gatherings with family dogs, if we are walking her, I will cross the street to avoid other dogs.

Last Christmas, our then four year old son, got down on his hands and knees and acted like he was eating her food with her. Had I seen this start to happen I would have never allowed it, however I was doing the dishes. She nipped his ear which bled. We spoke with our vet about this and instituted some precautions to try and make sure that doesn’t happen again, along with our son understanding that she is not able to handle that. Ironically, my wife and I could do that, and I have as a test, and she seems thrilled we are doing it.

Just tonight, I am traveling for work and my wife is on her way home from work, my mom is with our two sons, and our five year old opened the front door at the same time someone was walking by with a smaller dog, our GSD ran outside and “attacked” it. The dog walked away, but I do not know the outcome.

We are truly at a loss for words on what to do with her, we have spent a lot of time, money, and emotional resources on trying to protect her from herself, as well as our children and other dogs.

What is most frustrating is that she is such a friendly dogs to humans, and lives in a household with two loud, chaotic, young boys. She is very loving, very well-behave (outside of everything I’ve just described). So much of our life is devoted to protecting her from herself. The stress of it all is really starting to take its toll on me. I guess I am just trying to put this into writing and try and get any advice from anyone out there. I don’t know where to go from you. Thank you for taking the time to read this.