Honestly, I'd show her this exact post and ask for her help figuring out a plan that works for you both. It articulates where you struggle well, and articulates that you don't want her to carry the full cleaning load.

Possible thing to suggest might be a division along the lines of the as-it-happens and the weekly big things. If you struggle to notice the small things, but can take on the big once a week clean of the floors, bathrooms, etc, that could take a big chunk out for her.

The division me and my partner do is that we do a blitz together when our schedules line up - just clean the place for a couple of hours together. It sounds like mini blitzes a couple times a week may fit more with your fiancee's needs, but it's important that you talk to her on that rather than just assume.