How do you teach someone to be clean & organized?

I would like to know how does one teach someone to be neat and organized without offending them? My roommate and I had a discussion yesterday and voiced to her that it is obvious that our interpretation of, Clean and Organized, are different. Simple things such as picking up behind yourself and cleaning the shower after use have been problematic between us. In truth I feel as though my roommate is content with a messy home and detest a clean and organized home. In truth I am finding myself trying to do whatever it takes not to come home. I can not even get up in the morning without worrying about stepping or tripping over something. My question is simple, how do you teach someone to be clean and organized without offending them. I mean I am still emotionally upset when my roommate had her used tampons stuck onto the carpet and one was on top of the bathroom sink. I confronted her about this and she became offended saying, "I left it there for a second and I was going to throw it away." IMO this is just repulsive.