I was a lot the same when I was growing up, and letting the room stay messy isn't a fix for the rebellious behavior, and disrespect. I think she should have to be made to clean her room. I am now a single mom with two young boys, and they learn to clean up after themselves, ALL THE TIME. I don't let it go, I don't tell them we can do it later, and I never will. I think it's important that the respect you demand is given to you from your daughter as it should be. I don't know what types of privileges she has at this age, like TV, Computer, going out with friends, etc. But it would ALL end until she listened. I am a VERY strict mother, and I know that sometimes you have to do things to get your point across. If you go in and tell her to clean her room, and she gets online, I think taking the modem away was a VERY good idea...when she gets in bed after that, that's tricky. I would pour a glass of freezing cold water on her...but that's me...I do whatever works to get the respect I know I am deserved. My situation is different than yours though because I have two boys, no daughters, and my sons are very young. But I ended up living in group homes because I was such an out of control teen...and I often told my parents I wouldn't do something by either telling them to their face, or by showing them I didn't care what they said by doing something different. Either way, it wasn't the right thing to do. I wouldn't let her leave her room, even to go to the bathroom until that room was clean. I tell you, I am kinda oldschool when it comes time to get my point across, or time for punishment, I want it to stick in their head, that if they choose to defy me, or disrespect me, they will have it in for themselves...and they will wish they never had done those things. I wouldn't just take her privileges away until she gets her room clean either, I would take them away for a week. A solid week of no computer, TV, friends, etc would probably get your point across. And if she just tries to go to bed, drag her out, and make her do chores around the house. Being a mom of 3, I am sure there has to be plenty to do in your household!
Anyway, there's my two cents...and then some!
A.