This must be very hard for both of you. Financial stress in marriage can cause a lot of negative feelings between partners.

My advice is to take a deep look at everything your money buys... from morning coffee at Starbucks to groceries to car insurance to credit cards. Every monthly bill and subscription service fee to housing payments. This is the start of a budget. I'm not suggesting you cut expenses, I'm saying sit together and look at everything that you pay for. Don't forget to include the expenses that go on a credit card. Some bills may not be paid monthly (quarterly car insurance payments, annual hoa fees, bimonthly sewer bill payments, etc) Write them all down, how much it is, how frequently it paid and how it's paid for.

Create a budget that you both agree to follow. There could be bigger problems than just overspending or not keeping track of things. It can be very confrontational between marriage partners to deal with finances. Sometimes a financial advisor can be really helpful to mediate between partners in creating a budget. This isn't a her side vs his side issue... this is a we need to work on this together and find a solution together issue. Some employers offer a variety of employee services for free or at a reduced cost. My last employer offered 2 free sessions with a financial planner every benefits period. It's worth checking into.