Joint account is the problem.
Bills are paid, from any account... and her money is her business and my money is my business. No explanations required. She has the stability to know though that money will never be an issue. In some cases it could be a stress, I can see that. I'm lucky i guess.
I have a joint account with my wife from which primary bills are paid, but only some of my income goes there, namely my salary gets deposited in that account. But I also earn bonuses and have rental income and income from a small side business none of which goes through that account.
I also have hobbies that involve buying and selling pricy items, for example, firearms. Many of these items are a couple grand. Result is there's constant cash flow in and out of my own account. Any hobby like that which involves buying and selling something will involve cash flow. Buyb something on a credit card from a store, sell it to a friend for cash, etc.
The side business is similar. It requires working capital and the more I put in, the more it makes, a small margin. So it's normal for me to transfer money to it, and then over time transfer money back from it. Eg, put I'm $10000 and the business will eventually turn that into 12000. That money flows out of joint accounts but the returns come back through other accounts, even the return of capital.
I think an accountant would have trouble tracing my cash flows, my wife hasn't got a chance. At any rate I have enough money flowing through enough accounts that I can spend on whatever I like and she won't see the transaction.