I had a similar type classmate in high-school. Everytime is was her turn to host a sleepover I always said I was sick(which I do have Crohns). Truth was I didnt want to sleep in a house with a layer of trash over the floor, dogs and cats using the bathroom anywhere they want, spoiled food everywhere and bugs scurrying throughout the house. I would feel bad, because it was more her family that were filthy and she was the only one who would even attempt to clean the mess by herself.