Hi Doreen - That's a hard one. Is she the oldest?
All that we are required to give our children is a bed, a couple of outfits, shoes, and healthy food.
I think if my 12yodd didn't clean her room after being told to (being defient), I would remove from her room everything that was out of place and give it to good will. I've actually done this. The first time was hard for both of us because I hate to 'waste' anything. The second time they (9yo son and 11yo daughter) were probably trying to see if I'd do it again. I did it a couple of times after that, but noticed that they put their good stuff away.

I haven't had to do it in over a year.
When we have shower issues (or brushing teeth) they don't go anywhere. I tell them that I love them but I'm not going to expose someone else to dragon breath (Oh Yuck!) or sweaty bodies.
The clothes you buy her only have to be servicable, not stylish. Food you serve her only has to be nutritious. It doesn't have to be pizza or whatever.
The point is that you are doing all these things for her and she doesn't appreciate it, she expects it (I'm assuming) and would freak if you stopped providing.
If it is really bad (and I don't have a clue how intense it is), I would take every comfort out of her room and leave a bed, the dresser with a couple pairs of clothes, and pack the rest away - attic, storage, friends home. Let her live with what you are required to give her and she'll learn to appreciate what you aren't.
I know these ideas would work on my children (I know their temperament, training, and discipline over the years), but I don't know if it would work on yours, I don't know her - that's a call you have to make because your her mom.