Hi K.,
My daughter, now 15, had night terrors when she was younger. I was told not to try and wake her, and wait out the storm. Make sure she is safe, and keep close by until it is over. I know doing nothing makes us feel helpless, but the child will be alright, when it is over. I was always scared while they were happening, and thought she was "scared", but in reality she had no recollection of this ever happening, that is why it is so important to make sure the child is safe. If they have a bedroom upstairs, make sure there is a gate at the top of the stairs, just in case she gets up while having it.
Also, be very aware of what you put on the childs wall. Often, what we think is cute, or funny, to them when they are having these night terrors, is very scary. For example, I remember having a poster of a disney character on her wall, and at one point my daughter said "mommy get it off the wall it is too scary." Things look different to kids when they are half asleep then fully awake, as do they to us.
Hope this helps a little. -S.