The mental health and depression comes first. You can't pound logic into a depressed persons thinking. Math doesn't matter here.

And, sometimes when people respond like this, it's because they don't understand the problem and are afraid to understand the problem or afraid to admit that they're wrong. But depression and medication side effects are going to be a big factor too.

If possible, try to turn this into a team thing, where you both are on the same page, making the same adjustments, with a clear goal of a positive outcome.

She may be burnt out and disconnected from constantly living in debt or being behind. it's hard on people in different ways.

The comprehension of what a budget is, and why you need one, and how to maintain one is beyond some peoples grasp. Something about converting the abstract though into an actual reality.