Holy Night Terror, Batman!

I volunteered to babysit my niece, Olivia, a few weeks ago when my sister and her husband had late dinner plans.  When it was time to put her to bed, I thought she might put up a fight since her parents weren't there and she wasn't used to listening to me.  I followed the usual routine that my sister had told me about, however, and everything went well.  She was sound asleep by 9pm.  I went to the living room and laid down on the couch to watch TV until my sister got home.  Around 10:15pm, I heard crying from Olivia's room.  I went in there to see if she needed something, and the crying got intense.  She was wailing and screaming and inconsolable.  I kept trying to ask her what was wrong, but it was like I wasn't even there.  She was flailing about and trying to get out of her bed.  I picked her up and held her, but the screaming continued.  I realized that she was probably having a night terror because she wasn't awake.  She didn't hear my talking and didn't even recognize that I was holding her.  I wasn't sure if I was supposed to wake her up or not, because I'm no expert in handling night terrors!  I just kept trying to soothe her and rock her back to a calm state, but it really was just a waiting game.  After a few stressful minutes had past, she calmed down and stopped crying.  I put her back in her bed, and it was like nothing had ever happened...in her mind at least!  I was a little bit traumatized, but glad that we had gotten through it.  I felt so bad afterward though, like something I had done earlier that night had led to this event.  I told my sister about it when she got home, and she assured me that it had happened before, and I handled it well.  Thank goodness!  What a crazy phenomenon those night terrors are!