By management measures I mean looking at the environment - the physical set-up, the daily household routine, access given to the dog - to implement safety measures that lessen the chance of occurrence or impact of unwanted behavior. Management measures are a bridge, not a solution.
To truly help the dog you need to figure out the 'why' of his behavior, then use that 'why' to teach him more appropriate alternative behaviors to replace the unwanted one(s).
Controlling the environment is a quick change that buys you the time you need to address the root cause of the dog's behavior. Behavioral rehab can be a long and winding road; while you are working on it you want to set the dog up for success, that you don't put him in situations you know he can't handle, that you keep everyone in the household - two and four footed - safe.
A very important caveat:
When dealing with a situation that has the potential for conflict, we must be careful when giving advice. We forum posters don't know the dog or the owners, we have not seen the behavior and the various factors that influence it. Specific advice offered from afar, without fully understanding the whole situation, could be not only potentially ineffective but could also be potentially dangerous. Situations like these need to be assessed in person - and preferably by a trainer or behaviorist, someone who is qualified to assess all that is involved in the behavior. This is why I am so very glad to hear that your friend is seeking professional help.
Strangers over t'internet really cannot offer much more than general advice. We can discuss our own experiences with our dogs in superficially similar situations - perhaps something in our experience might give your friend ideas as to how to think about her own situation. But I must stress that any advice given here should only be treated as background.
---
With that caveat in mind, management measures in a sort of similar situation:
One of mine has an issue with over-excitement going out of a doorway. Another knows how to open the screen door himself and so will barge ahead to let himself out. If both are trying to go through the door at the same time - WWIII, with the first dog kicking it off.
It's fairly obvious that the underlying problem is not just going out of the door, that is only a symptom. Rather, I have a dog who is unable to handle excitement, which might lead to displacing onto the other. I also have a dog who needs a bit of remedial manners training. These take time to deal with, the former perhaps a lot of time. Meanwhile I need a safe going-out-the-door routine.
The immediate management is restricted access. There is a gate in the kitchen, only one dog is allowed in the room with the door at a time. The other waits, having been given something interesting to do while waiting. Dogs go out singly, on lead. No trigger, no WWIII - I do not let the dogs get into a situation they cannot yet handle.
A babygate, leads, consistent routine. Management diffuses a potentially dangerous situation in the short term, buying me time to work on the real issues. I hope I don't have to manage the situation to this extent forever, as it isn't easy to live this way. But in the short term I do what is needed to prevent conflict.
In the case of your friend, she should think about how she might be able to make changes to the set up of the the house, to her daily routine, to make it safer in the interim. Is the guarding only the son's room? If so, in the short term can she restrict access to the area of the house, that the dog guards? If the guarding behavior is somehow connected to interaction with the family, can she make changes to the household routine wich might lessen the frequency of triggers?
And then focus on finding a trainer or behaviorist to begin the real work.
---
FYI when working with a trainer or behaviorist it is often helpful to start out with as much information as possible. What, where, when, guesses as to why - noting any patterns that seem to crop up can be very helpful. Often a video of the unwanted behavior, with explanation as to what happened immediately before, can be helpful in diagnosing root causes.
If guarding behavior seems to be linked to something in the household, it is often helpful - perhaps necessary - to have the trainer or behaviorist see the situation at home. Finding someone who can do an on-site assessment is often recommended.
---
Another possible resource, Edith Streuli:
https://www.certodog.ch/hundeschule/edith-streuli/
I have worked with her a few times, recently in a 1-1 with Robin Goodfellow and Heffalump. She and my trainer are close colleagues - often additional eyes on the problem can be helpful.
The link above is from the Certodog listings. Certodog is an organization of dog trainers in Switzerland. You might browse through the list of trainers for someone convienient to your friend. You can assume German will be spoken, other languages are often mentioned in the trainers8217;s own website.
https://www.certodog.ch/infos/hundeschulen/
Hopefully other EFers will come along with additional suggestions.
Again, wishing your friend all the very best.
ETA:
Aaarrrrgh! I hope a solution for the new problem where numbers are inserted for apostrophes is soon found. In the meantime, I hope the above text isn't too unreadable.