Imagine getting a knock on your door with someone outside yelling, "Open up it's the police." After you open the door, the police officer points a pistol to your head, and that's when you realize that this guy is a phony and that you"re in trouble. This seems as though you"re watching a movie, but that's exactly the way D.H. Lawrence depicts Paul's mother in "The Rocking Horse Winner". In the very first paragraph he mentions that she covers up her faults in the presence of her children. Everyone also considers her a good mother outside her family; while the facts is that she is very bitter. As a result, the mother's character in the "Rocking Horse Winner" is portrayed as deceitful. .
One explanation for the mother's deceitfulness is her lust for money. She never budgets her money, causing her to constantly run out and need more. This triggers a major conflict within her, which influences her family, to a point that the house becomes haunted and the kids begin hearing the house utter, "There must be more money! There must be more money!" As a result, the mother becomes very insecure. Usually when a person is in such a miserable situation, his self-esteem is lowered greatly, forcing him to lie and be a fake. This is the case with Paul's mother, and this is why she's depicted as phony. .
Another interpretation of the mother's fake behavior is, perhaps, that her parents are a pair of phonies themselves. They bequeath their characters to their kids; hence the mother is the way she is. Both, her mother and father don't love each other, so Paul's mother also feels she can remain married without love. Her parents, probably, seek to hide everything from her, as does Paul's mother with her kids. Therefore, the mother's personality is all a matter of inheritance from her parents. .
Furthermore, a possible analysis of the mother's character is that she is spoiled when she is a child.