Tell the roommate you all get even 1/3's. Look her in the right eye (something to the right eye) and say, "Don't you think it is fair if we all have even 1/3 of the space?". wait for her response. you speak first, you loose.
If she has reason for her to get more than her share. Express you feel the same way and right eye her again, and express to her that you are not going to give in on this one. Don't swear, it is a sign of loss of self control. Don't raise your voice, and talk a little slower than normal. Maintain self control to get situation control.
For everything she tells you that would give her the advantage, strongly but firmly, remind her you would like the same advantage, but it is not right for either of you to have more than your share "correct?". Right eye let her speak. Maintain your control. If you can not agree on 1/3, 1/3, 1/3, then everyone has all of their personal property in thier room until fairness has been reached....even if it means hauling that printer in and out several times a day.
Then buy her a sleeping mask and inform her that you need the night and the quiet to study and she can learn to sleep with a light. She started life that way, and she can continue life that way. right eye and maintain self control. Don't swear and remember you are the older one. You mother her. She most likely is spoiled at home and expects you to spoil her. We all live life according to the decisions we make. She needs to learn that the selfishness may have worked when she was a child, but it doesn't work now. Time for her to grow up. Life will not be handed to her in the future, and it is not your job to hand it to her now. Get control of the situation or live with it. Don't let her scream and yell to try to win the situation over. If she raises her voice , lower yours even more and ask her how she thinks yelling will work.
If you don't control the solution of the situation, she will continue to control the situation.
If you need to, bring in someone from the school to act as mediator. Both of you agree to do whatever the outcome of the mediator says as your solution.