Your instinct on your mom's searching your purse might be prejud
Human beings come to instincts at averse situations to avoid the worst risk. You would run away with no hesitation when a tiger staying in a zoo cage jump towards you. Knowing the tiger is blocked by the cage would not help you because such instinct has been built in generations.
I wouldn't bother to analyse why most of us have the same instinct when we see another is at intimacy to our privacy. There is a recent example too. When Ravi turned on the video camera at Clementi, the instinct of some, if not most, opened up a Hate Crime. I am not arguing that it was not a possibility. It is a possibility with the lowest probability. Most probably, it would be curiosity. It was unfortunate that it is the curiosity that also has killed a cat.
I suggest you run away from your this instinct before it kills the family. In this case, that your mom is a family member of you is the cage. But this didn't help you coming to a harmful instinct. If you keep this instinct, it sure will ruin the cage--the family relation. By then, your instinct would become a reality.