I have a wonderful friend of many years, and I go to visit her every six months or so (we don't live near each other). I love her like a sister, but she doesn't dust or vacuum, and everything's covered in dust and pet hair. She also smokes inside. I've always found the air in her house unpleasant, but I tolerated it for the sake of her company. Two months ago, I was diagnosed with asthma. I had to be hospitalized and I still have symptoms every day. There is no way I can visit my friend's house the way it is - but how can I tell her so with a minimum of hurt feelings?