I'm going to ask my college roommate to stop sleeping on the futon
Why don't you want her to sleep on the futon?
I refuse to allow her to be more comfortable than I am.
I understand that you want to be able to sleep comfortably, but you can't tell your roommate where to sleep. If the futon is your roommates, let her sleep there and you need to sleep in your own bed.
I do not understand how you are not agreeing with me. It is weird.
It is just the fact that your roommate is the owner of that futon. For this reason, it makes no sense for you to tell them that they are not allowed to sleep on it. They also live there, and should be free to sleep where they want.