Because I live in a dormitory, several people share a toilet, and I go to the toilet for a minute ev

First, you need to observe if you have offended them in any way. Second:

You can pretend to try to ask them if they want to go to the bathroom, and then they knock on the door when you do, and then you have to be bold and say to her: What do you want? Where have I offended you?

If you deliberately do this while you're in the toilet, it's infuriating. Did you offend them in any way? If not, it may also be a coincidence, a joke. The dormitory is different from home, so don't rush too much about some things. After all, if you live in one place, you will see each other in the future.

Before taking a shower and going to the toilet, ask them if they use it, use it, don't go by themselves, and don't worry about themselves if they use it slowly.