It could have to do with the
Bank Secrecy Act (see
https://www.money-education.com/res...ng-cash-transactions-under-10-000-is-criminal ) which deals with money laundering, drugs, and other nefarious activities by businesses or individuals. If a cash amount over $10,000.00 is deposited or withdrawn at a US Financial Institution, a Currency Transaction Report (CTR) must be completed by the transactor and the bank/financial institution with whom the transaction(s) is/are conducted.. The bank/financial institution will file the form and send it to the US Treasury Dept.
If you vary your deposit/withdrawal into sums of cash lower than $10K (2 deposits of $7K each, for example), then that is seen as "structuring," and that is also illegal. It's not the cash that will get you into trouble (if you're running an honest business), it's the non-filing that'll getcha. I was a programmer/developer at a US bank for years, and I supported the system that analyzed the cash transactions.
So it might be that she withdrew $30K in amts less than $10K to avoid completing the CTR report, and the bank's analysis of deposits discovered it after the amounts totaled more than $10K. Anyone familiar with cash amounts at banks would know about this regulation -- it's been around since 1970.
More than you wanted to know, I'm sure, but it's just a thought... I don't put much past that IMO scheming woman.