I am a gradute student and at the clinic where I work we weren't really assigned any office. The professor said we are free to use any room and share offices with each other. There are some older students who have been here longer and kind of got used to using the same space, which they call "their office" although they offered to share it with them. Since I am new I figured to use this one office that noone was really using. It has an old computer, but since I'm not picky, I figured I'd use it. In the meantime, the computer crashed and moved in a different room. The older student who usually uses this room is not here often, so I figured this is a good one to use. Things went well and I was fine with moving my stuff if this student wanted to use the space because she had appointments etc. Now, another worker comes into picture who is not a student but was hired as a therapist. She uses this same room, too although she also used a different one. Now, the student who used this different room came in today and the therapist had to move. Where? In the same I was using...getting ready for my appointment. She asked me if she could use the space I was in and I said that I was expecting someone and they would come at any moment, therefore she had time to set up her stuff in a different office. In the meantime, she goes to this other older student whose room she was using in the first place and she told her I should switch offices coz the clients got used to having the sessions in one room (which they actually had sessions in both and I'm sure they don't mind what office they go to as long as they get help). She said clients in therapy come first and if I have an assessment I should move. I don't understand why she did not move as she was doing work on her computer and not seeing anyone. In the meantime, I had to rush moving things from one room to the other. At the end, the therapist said she'll be using that particular room from now one. I told her we are supposed to be sharing offices and unless she has treatment, I'll use that room. Now it may not look like a big deal, it's just that I spoke to the student who uses the room more often and since she'll be gone for the summer, I figured to put my things in there.
I would like to know how to deal with this situation. This lady also checks on me and another student whether we get to work on time, although work is flexible and I stay over my schedule and there is an unwritten understanding that it is ok to be 10 minutes late when the night before you stayed 2 hours over schedule and did not mind and you actually LOVE your job.
Also, the student who suggested that the therapist uses my space instead of hers has days when she is mean and others when she is extra nice. So, I don't know how to behave around her. I feel like I should ignore her, but then, we are students, I am here to learn, and I don't want to feel intimidated by anyone. I want to learn to be assertive and say things w/o hurting other people, but sometimes I feel people are so strong headed that is hard to deal with them.

Any advice? Thank you.

P.S. Is there an "edit" option still?

I don't think you can really get ahead in the clinic you mentioned, unless you stand your ground and try to create some sort of egalitarian environment by being somewhat assertive, but not overly so (if that makes any sense) because you don't really want to piss them off.
Just show them that they're not better than you.
If all fails, you should probably contact a higher power.
No one deserves to be bullied in the workplace. It's depressing.