Much as I get your thing with the mother-in-law from the rant thread, I've actually seen good use for that triple set. My aunt uses a triple crock pot set to cook sides; ex: today, one had mashed potatoes, another had a green bean casserole, and another had... I can't remember, but it's probably in my fridge. There is a way of using them.
I'm lucky I only got hand-me-downs from my family--they expect us to eventually replace the stuff. Unfortunately, if you don't have a use for them, you'll probably never be able to get rid of them since she'll be looking for them to be in use whenever she comes over.