Question about how to do this discreetly

take extra cash out slowly while shopping $50-100 at a time

Go to like rexall, shoppers or any place you would go normally purchase 10-15$ of what you need and ask for a cash back of like 40$ each time and build up each transaction.
If your SO ask why you go to shopppers so much and its 50$ each transaction, say you bought immodium or those allergy pills lol. Both are expensive

Take some cash out and when she asks ,you bought lottery tickets,lunch off a street vendor,went for a beer with the boys.....it will add up.Better yet start buying and selling stuff online ,and build up a stash..

a decent place to hide cash so she wont find it......in the spare tire well of your car, you will have it when needed

Other common places that offer cash back: Walmart, LCBO, Home Depot. (Just go $20-40 at a time, and it probably won't get noticed.)

You could also open up a second online account at Tangerine or one of the credit unions, then direct your employer to send a small portion of your income to that new account each pay period. (Perhaps wait until a pay increase or new job to avoid any suspicion.)

Do you have just one source of income? Can you get your employer to split your pay into two accounts? Just say one account is for your mortgage payments and you want to keep it seperate.

What do you pay cash for now? If nothing, start to gradually use cash, make sure she knows about it. Got any stuff of your own that you no longer use that has some value? Sell it.

PM me if you want more advice.