You need a schedule. I have the same problem - I don't really notice mess until it gets out of hand. So you can't rely on noticing it, you've got to have a habit of checking. While the coffee is brewing, are there any food crumbs on the kitchen counters/dishes in the sink etc. If I get up to go to the kitchen, I scan the room I'm in for any dishes, any rubbish I need to throw away. While dinner's in the oven, do I need to run the hoover around and so on.

Maybe discuss with her what she's noticed you're slacking on and make a habit to check frequently if you're doing that or not.