Having read this thread, I am wondering whether your cat's behaviour is being triggered by a memory of something in your mother's posture/smoking by the door/door being ajar/what your mother is wearing - clothes/perfume, etc. You mentioned that when your mother had showered your cat is OK again. This may be pointing to something scent-related, e.g. smoking, something you mother has touched en route to your home, her perfume...?
Hope this helps.
Hope this helps.