I hate my grandpa so much!!

Okay so my dad has a uncle who has a business, and since they have limited employee and need someone to help them run the business, they ask my mom to help them so my mom politely agreed to help them. (Keep this in mind, my mom teach me not to steal anything and be truthful all the time so I know she would never do such a thing and she is not that type of a person she is kind and support all of my achievement) So she has been helping them run the business but after a week they start being so strict they check the storage all the time or the receipts INFRONT of my mom, even tho there were not any missing or miscounted things, and it feels like they're assuming that she would or will steal something BUT GOD KNOWS HOW MUCH A KIND PERSON SHE IS. Should I or my mom feel offended or is that normal to be that strict if you have a business??