Is my daughter too young for haunted trails/houses?

It sounds like she's ready, I say you should give it a try. Remember that these things are supposed to make people scream. I'm a scaredy cat, so I screamed my lungs out my first time on a haunted trail. However, I wasn't having nighmares that night, because, after the initial scare, you know it's not real. Remind her of that, and I'm sure she'll be fine. The choice is yours, however, and you can be the judge of if she's ready or not.