Someone's stirring up the Bees Nest about "you" doing the work at Self-checkouts

My future sister in law was at a self check out and an item didn't scan properly. A few days later she gets a knock on the door and was cited for retail theft!!! They have her on camera "stealing" the item , then they got her plate off the parking lot camera , then called the police to "track her down" We're talking a $2 or $3 dollar item not a t.v. She absolutely made an honest mistake and was treated like a criminal over it. Since I'm not PAID OR TRAINED AS A CASHIER THEY SHOULDN'T BE ABLE TO EXPECT ME TO DO IT WELL???
I'm surprised about that. Law won't even prosecute anyone unless it's a grand