There is no sure-fire simple way to solve this problem. There could be many reasons: frayed or shorted wiring, bad connector(s), defective fusebox, bad switch, or a combination of these things. The only way to fix it is to do a thorough step-by-step examination of your electrical system. That means crawling around under the car, looking under the dash and engine compartment, or even removing some of the automobile components in order to be able to view some of the wiring hidden underneath (for example, taking out the instrument cluster).
If you have never done this before, you are at the mercy of whomever you hire, so hire someone you can trust. Not that they are dishonest, but a dealership is the last place I would try because of their high labor rates. Happily, I am fortunate in that there are very reputable small "Mom and Pop" foreign car repair facilities in my area. If you don't have the luck to have one of those nearby, and you can't do the repair yourself, then your only choice is to take it to a VW dealership. It'll cost you more, but at least you'll get it fixed.
As to the possible effects of not getting it fixed right away. That should be obvious: a fire in your car, or worse. You shouldn't allow your mother to drive that car in it's present condition. She could be killed, and/or kill someone else on some dark night when the lights suddenly fail. Beyond that, she could be the victim of a car fire, day or night.. So I suggest that you park that car until it can be towed to a repair facility. In the meantime, be sure to disconnect the battery.
By the way, a "loom" is just another word for "wiring harness". The loom (wiring harness) runs all over, under, and everywhere in and outside the car.