Hello!
The answer is: She should check her own records to see if she made a mistake
Why?
It's most likely she made a mistake when she took her own records. Most banks have verifying systems that check every transaction and if it finds a mistake it will fix it automatically and it's probably that she does not even notice that.
If she is right and there is a mistake with the bank's records she should go to her bank and ask to discuss her account with a bank officer, it's probably the best way to solve a problem related with your bank account.
Have a nice day!