ESL Discussion

Today I will talk you a story ”Drag”.
Cam and her sister Oliver bought a business from their mother twenty years ago. The business is a dog-cleaning business. Every year they paid their mum 1000 pounds of the gold. They all love and respect one another. The daughters will finish pay off a business in two years. 
They have a problem. Their mum, who is 77 years old, gets a salary from the business above and beyond the payment from them. Her work is dog-cleaning. She uses a toothbrush to wash a big dog because she was too old and her hand is very small. She doesn’t want to wash a litter dog. Her workload has lessened greatly, as it should. She could do all her work in one day and lessens a burden of her salary. If they discuss this, the mom get hurt and says: she would go crazy, if she retired. Her daughters don’t want that. The mum still comes in as often as she wants and does her personal: paperwork, banking, letter-writing, reading… on the clock. The daughters would hope that she would see the fairness of this and suggest it herself.
Business expenses are going through the roof. They are very boring in the situation/
How do you think why their mother only washes big dogs?