L.M.
Although my daughter was never diagnoised with "night terrors", I believe she suffered from them. She would start screaming in the middle of the night, sometimes her eyes would be open, but I know that she was sleeping. My daughter was younger arround 2, and she did out grow it.
I would go into her room and very softly and calmly say "Mommy's here, everything is okay", being very careful not to wake her. After a few minutes she would go back to sleep.
I would recommend keeping a log of when this happens and how long it lasts. Then speak with the pediatrian and your counselor. They can give you some expert advise.