I didn't have night terrors as a child but started getting them when I was older. I was told that my psychic abilities had "popped open." I had to sleep with some light in the room so I could distinguish between this reality and the other.
When we go to sleep and go into REM, we dream - basically we go traveling at night and because we are in our spiritual bodies, we don't fear any of the stuff we see. So all that scary stuff is normal; it's just our waking consciousness doesn't know what it is and is terrified. What I think happens is that we wake up before we wake up - meaning we wake up on the astral plane before actually waking up in this reality (if that makes sense.) It's like the brain gets confused on the waking and dreaming states.
I can only tell you what worked for me and that is meditation; it seems to calm the brain waves. I also recognize certain triggers; for example, if I'm upset before bedtime, that will often trigger an episode. I know that there is information online for helping children to meditate. The other thing that might help is to find out what relaxes her - a bedtime story or certain music. You might check out Hemi-sync or binaural beats, they usually have some on Youtube and are often within relaxing music. They help to reduce stress; I don't know if they work for night terrors but it's worth a try. It's just a matter of getting her brain to relax.
Also, whatever methods you decide to use, it may take several attempts. It's terrifying to go through it and that fear of going to sleep can create more fear. I'm glad you understand what she's dealing with.