Obsession with lucky numbers as a magical manuver to avert disaster/death

A lady who suffers from severe anxiety and quite a few obsessions brought up her fixation on number 5 in the session. "When it comes to numbers I have to do everything in multiples of five to avoid disaster."
The ostensible reason that she gave was that by bringing in the number 5 she converts bad luck to good luck.
An example she gave was her going to a horse competition - she is an avid horsewoman - where her horse was given a tag with the number 164. She immediately began worrying that it had no 5 in it, and that meant ill omen. But then she found an ingenious solution. She reasoned that if she subtracts the first number (1) from the second (6) it becomes 5. And as far as the last number is concerned if she adds second number (6) to the third (4) it becomes 10, which is a multiple of 5. And with this calculation she knew she was in good hands. And with this confidence under her belt she could singlemindedly devote herself to lead her horse to victory.
What lied behind this obsessive mathematical exercise?
Now she has two brothers, and if we count them, herself and her parents, the total comes to 5. Was the obsessive invoking of the number 5 a ritualistic way to protect her family? She did not affirm or deny this psychoanalytic construction, but indirectly confirmed its correctness by immediately adding that just like number 5 is good, the number 3 is unlucky for her. She hates 3 and its multiple 6, 9 etc. and has to replace them with 5 to turn bad into good.
The associations to number 3 brought her parents divorce when she was just 4. She made sure to immediately claim that the parents divorce made no impression on her. She was too young to understand it or be bothered by it.
This pricked up my ears, because we know from Freud that obsessional neurotics often reveal their deepest secrets almost as a non sequitur with hardly any emotions. They will say something like "Oh by the way this thing happened, but I never paid much attention to it." What they are saying is that what I just revealed is the core of my problems, but to protect myself from it I have drained it off of all its emotional energies, and so now it is remains in my psyche as a colorless memory towards which I behave as if it has no significance.
So I deduced that the divorce did matter to her, but she sequestered it and stopped giving thoughts to it.
"So did anything bother your about your parent's divorce?"
"What bothered me was my father immediately marrying my step-mother. Hardly a few months after the divorce she was there in our lives. I hated her as an intruder [third person] in our lives.
She then proceeded to tell as to how she never hated her mother. A psychoanalyst has to ignore the disclaimer and take the statement at face value, ignoring the negative prefix, and saying to oneself, "She does hate her mother."
She confirmed this by quickly going on to tell me went on to tell that she may not have hated her mother but she absolutely hated having to move into her grandmother's house, where she had to share the same bedroom with her mother, and had to sleep with her in the same bed up to the age of 16.
"Who else you hated?"
"I hated my grandmother. We had to live in her house. She was mean. She tried to suck the life out of me. She could not stand my taking interest in anybody. Even putting on the lipstick was treated as something horrible."
So the three women, all who could be put in the category of mother, she hated, and it was this hatred which was hidden behind her detestation of number 3 and its multiples. The appearance of my mother, step-mother, grandmother spells disaster for me was the unconscious reasoning.
"Does the number 5 protect you or your loved ones from evil and death?"
"I don't know that," the patient replied, "But whenever I hit a bump from one side of the car I have to find a bump to hit from the other side of the car to even it out, otherwise I fear somebody close to me will die."
But if the people she hated were her mother, step mother and grandmother why would she wish her brothers and her father dead , if we assume that the use of number 5 was to protect them from her death wishes?
Here we recall that she has the obsession to bump the car by the other side if one side hits a pothole. This was easily confirmed as a reparation for the death of one parent by balancing it out with the death of the other. Her death wishes towards her mother was balanced by equally strong death wishes towards her father.
Her brothers who were many years older than her were loved and resented at the same time, for they reminded her of not being the only child.
So this obsessive young woman was plagued by death wishes towards both her siblings, and her parents, and as a punishment for these evil impulses, death wishes towards her own self. And with the aid of number 5 she could save them from her feared destructive impulses.