I Need Help

Hey! I have a question for some other survivors- this is my first experience dealing.. I'm a rape survivor with PTSD and I am going on a school trip that will lead to me sleeping on the bus (overnight bus rides.. yay) and I get flashbacks in the form of nightmares very often, and I can't wake up without being roused (usually, I'm trapped in the flashback until my alarm goes off). Is it safe for my teacher or friends to wake me if they see I'm having a nightmare? If so, how should they do it? I'm worried that in the midst of my flashback I'll forget my surroundings and possibly view the person waking me as a threat. what are some things they can do while waking me and immediatly after I wake up to help?

thanks xxxx