Good news: You are definitely not being unreasonable.
The really good news, though, is that as an adult you get to decide these things for yourself. It sounds as if your mother has tried to take this choice from you to maintain her power over you. It will not be easy for you to claim it back, but it is simple. Choice is like a muscle, it gets stringer the more you use it.
Start small, inside your own head, ask yourself really simple questions. What kind of toothpaste do i like, do i brush my lower teeth first. Really easy things, check that you are doing what you want and in view of the consequences and then build up to question of the things you do to win/keep her approval. That game, winning her approval, is a mugs game that she makes you do to keep control over you. Now is your time to kick over those traces.
If she objects, nod and smile, don't engage and live your life as a demonstration of your own choices.
Choice, given the consequences: welcome to your adult life. Its going to be great and it will be all yours.