If you are already resident in Switzerland you may not import a (surgically) docked tailed dog.
The one time exception, for a family moving to Switzerland with their family dog traveling at the same time they do, does not apply if you are already resident here.
A natural shortened tail or natural lack of tail is allowed... but if questioned the burden of proof is on you. Be aware if this is a breed where docking was common more scrutiny might ensue.
Now... is there any 'compassionate' leeway?
You will have to contact the Veterinäramt in your canton with the details of the situation and ask for their ruling.
My experience via our rescue work has been no exceptions granted, even for a dog who was the victim of a horrific attack that resulted in the loss of his tail, a breed that has never held docking as a conformation standard - which is what the law is trying to combat in the first place.
But as with everything in Switzerland, YMMV. Put your case together as sympathetically as you can, and see what the Veterinäramt has to say.
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I do know of one person who when faced with a similar dilemma deregistered and left Switzerland to move back to the US to take on a family member's dog, then moved again to Switzerland a year or so later, taking advantage of the usual family dog exception. This, however, was many years ago.
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IMO and IME, it might be prudent for your mother to come up with a Plan B, as difficult as it might be for her. How to provide for our beloved pets after we are gone is a worry many of us face, so I sincerely empathise.
All the best....
ETA:
In post 33 of this thread, Patxi wrote about importing a dog with a congenitally short tail:
https://www.englishforum.ch/pet-corn...la-c-te-2.html