Is my Suitemate just very difficult to deal with or am I being a jerk?

Wearing shower shoes and covering the toilet seat aren’t a reflection of how clean the room is. Maybe you should quit evaluating her personal habits. They really aren’t your business.

Does each room have a thermostat or just yours? If the only thermostat is in your room, how was she supposed to change it without going into your room?

If you expect her to make changes then you need to be willing to make some too.

You can’t make her “deep clean” the bathroom every week. And you don’t get to “criticize” other adults and expect them to change their behavior because you said so.

Have you tried sitting down and talking to her? It sounds like neither of you are communicating very well. She can’t read your mind. You’re going to have to talk with her and be able to make some compromises as well as ask for them.