Ask yourself this question: what will happen if my daughter doesn't clean her room? I can answer that for you: nothing. Just close her door don't bother yourself... you have enough of your own stuff to worry about!
Try to remember that all kids are different temperments. Some kids are "neatniks" and others are "messies". If your kid is a messie, she may be that way forever and grow into a responsible, loving, messy adult.
If you really want her to clean, tell HER to pick the one day (same day every week) that is "clean-up" day. Afterward, she can have a reward, like you two paint nails together, or watch a special movie, or play Twister, or whatever. THis way she has some control of the situation and it is more like her decision rather than yours, although you are actually accomplishing what you want. If she doesn't clean her room she doesn't get the reward and she can't earn it until the following week on that same day.
Once again I would say, pick your battles. Show your daughter that her attitude, manners, honesty, etc. is more important than being able to see her floor. And when all else fails, use a garbage bag while she sleeps. That's what we do.