I'm going to have sex in my friends bed and leave her house messy.
Why do you want to leave the house messy?
I can't find any reason not to leave it messy.
Having sex in your friend's bed and intentionally leaving a mess at their house is not a good thing to do. It's very rude and disrespectful and will make your friend annoyed with you. They may even be so annoyed they never invite you over again.
What is the big deal about not cleaning up?
It would upset your friend to know that you did not care about her place and in a way did not care about her. You could lose a friend for not respecting her and her things.