Air conditioning in winter?

Hello,
I know thermostat wars are very common with roommates, but when I look up this issue I can’t find anything similar to my own. My roommate likes to turn the air conditioning on in the winter. It will be anywhere from 20°F to 50°F outside, and she will turn the air conditioning on. We have an older thermostat, so you have a heat, off, and cold option. I’ve tried talking to her. I’ve told her of the temperature outside is colder than 60°, it would be more effective to just open her window. It’s just her room that she wants cold, but the rest of the roommates end up suffering. I believe she likes it this cold because she lets her boyfriend live here. We live in on-campus freshman apartment style dorms, so the beds are made for one person. My roommates and I believe they get hot crowded in the tiny bed, and turn the air on.
It’s getting ridiculous, no matter how much I talk to her, when by compromising and saying we can leave the heat off period (at 20° outside), she doesn’t listen. I will wake up in the middle of the night shivering and feeling sick, to find that the air conditioning is on. Sometimes she will cover the thermostat in tape thinking we can’t touch it, but she usually just sneaks and turns the air on while we are sleeping. It was snowing yesterday, and she had the air conditioning on. I’ve exhausted my avenues of communication, and it’s getting to the point where I fear my health will be affected. I don’t know what to do.
Additionally, heaters are not allowed in my dorm complex, or any other portable heating element.

Have you asked for outside help from an RA, for example?

Agree, engage the RA.

Talk to RA. Schools are not interested in spending money on heat or cool rooms that are not appropriate for the outside temperature. Temperature inside is generally about 68 to 70 degrees. There may be some way to lock the thermostat. To keep yourself warm, add blankets that are fuzzy. Right now a good kind of blanket is found at the grocery in patterns and tied with ribbons. Cheap. Put some under you and sleep in one folded, add one of two to top. I am always cold and find these blankets or throws are lightweight, soft, quick and easy to wash and dry. You can and must control the temperature of your bed.

Definitely talk to your RA. Say that you have spoken to her directly about the issue. Schools want a general range of
temperatures for safety. Also say that you think her boyfriend is living there full time. That should not happen.