I first went to WDW when I was 5. My parents brought me on the Haunted Mansion-and the ominous atmosphere and structure had me terrified. Then the doors opened, and I saw the portrait of Master Gracey decaying, and clung to my parents for protection. By the time the stretching room started to work its magic, and the lights cut, just as some kid's balloon popped, it was game over for me: I was sobbing and begging to go home (not back to the hotel, but home home). I remember being fascinated by the ballroom, and had my eyes shut for the rest of it. (I'm pushing 30 now, my parents still laugh about how freaked out I was.)
But here's the thing: the mansion became a fascination. I would draw pictures of what I remembered, and hung paper ghosts in my room. I almost wore out our VHS copy of Disneyland Fun watching Grim Grinning Ghosts safely under blankets over and over again. My dad made me a giant cardboard fort shaped like the mansion, and I colored a portrait of Master Gracey and hung it inside. The Haunted Mansion was my favorite thing about our trip, and I only really saw about 20% of it because I was so scared.
I'm not saying your daughter will have the same sort of experience I did, but Walt Disney and his artists designed his attractions, and his movies with the knowledge that on some level, children kind of like to be scared. It's all part of the magic-and while I distinctly remember checking behind me to see if Phineas really was following us home, I didn't hate the experience. I wasn't all for going inside again or anything, but the fact that a ride that terrified me so much is still my favorite 25 years later says to me that Disney is doing something right with this one.