It also comes down to how the person sees money. Many people I know look at payday as the day that they are rich. Myself I see it as 14 days until payday. However 2 days before payday I am "rich" because I didn't spend all that I had to spend.
I hear people at work say "let's go out to the bar- it's payday so I know you have money."
Those same people come to me 2 days before payday to borrow $20.
But a big part of this realization for me was that I know I am bad with money, so I don't let myself spend it. I have one credit card with a low limit, and I cannot use my savings account ATM card for Interac purchases.
Maybe a change is needed for the two of you. Take the gross monthly income, and set up the budget to pay the bills and whatever savings, and then after that
each of you gets an allowance. Heck; even give her $50 more than you. Each of you gets a seperate account with seperate cards, and that's the money that each of you can spend. Wait for her to run out of money, and then mention that you still have money left, and started out with less than she did.
This is all "single guy" advise, so take it for what it's worth.