If your mother prerinses everything she'd better start using less detergent. Perhaps half a W5 tab is more than enough. A full tablet of detergent will eat the innards of the dishwasher in the end.
A friend of mine, who prerinses religiously, had a motor destructed by his prerinse regime. The motor of his Miele dishwasher died after ten years. The first thing the Miele repairman asked was if he prerinsed. He confirmed that. The Miele man replaced the motor and said to him he would be back if he continued prerinsing. I think the dishwasher lasted another nine years, but he doesn't use it frequently because he is single.
My friend bought a new Miele dishwasher. I bet this one will not last longer than ten years. He is still prerinsing. And because the newer one uses less water, the detergent solution is stronger. Most likely he will have problems again.
I never prerinse. My AEG 6060 lasted 18.5 years. The motor was still working, I got rid of it because I got a good deal for a new Miele. And the racks of the AEG started rusting. The AEG motor was just as silent as the day I bought it!