Unfortunately, love does not always last in marriage. Love was a very important topic to D. H. Lawrence, as was the relations between mothers and their sons. The mother in "The Rocking-Horse Winner" was not a terrible woman. She would have been glad to experience love for her children and for her husband. She was more a victim of society. She had acquired false values, as many women do from attending snobbish finishing schools and reading about women who enjoy better lifestyles. She not only wanted better things for herself and her children, but she felt she was on a slippery slope and that her situation could get considerably worse. They were spending more than they earned, and it seemed impossible for either the husband or the wife to make more money. She was motivated as much by fear as by greed. Paul has the following exchange with his uncle.
"You know people send mother writs, don't you, uncle?"
"I'm afraid I do," said the uncle.
"And then the house whispers, like people laughing at you behind your back. It's awful, that is!"
The "writs" would be threatening notices regarding unpaid bills. She may have blamed her husbnd for his fecklessness. Financial problems are the cause of more marital unhappiness than anything else.
To me the mothers love turned to dust because she only had love for one thing, Money. She lost the ablilty to love because all she want was money money and more money.