I recently saw The Conjuring for a second time and have a couple-three observations you might find relevant:
1). While I said that I there is nothing in there you haven't seen before if you've seen a few horror movies, keep in mind: If you are a 10-year old girl who has seen NO horror movies, there will be a whole lot of things you haven't seen before.
2). If you are the above-mentioned 10-year-old girl, the scares will be quite intense: make sure you have an adult to hold on to, tightly.
3). If you are worried about having nightmares after seeing this movie, I have it on good authority that thinking about "ponies and unicorns" will help solve the problem.