You should watch your receipts, but this woman has abused the system.

There are reasonable ways to take care of issues.

I'm sure the system hasn't changed much in the ensuing years, but 20 odd years ago, the manager would print out the daily price changes in a batch, hand it to the stock staff, and have them make the changes. Now, you're doing this at 0dark 30, coffee hasn't kicked in yet, and being that the stock staff is normally teens/college kids, they may be more interested in flirting with the other employees and socializing than doing their jobs.

If the changes aren't made properly, the first notice the manager normally has is a customer complaining about the price not being correct.

Not everyone is out to screw you, but this plaintiff certainly seems to have a chip on her shoulder.