Fighting Over Sleeping with Mom and Dad

My 9 year old daughter comes out of bed every night because of a variety of reasons. Today she said she was afraid of someone murdering her (she has a great fantasy and isn't exposed to anything that could have sparked that). I was annoyed but tried not to show. I hugged her, calmed her and brought her back to bed. Later I would feel guilty and now I'm laying in bed and wondering if we should allow her to sleep with us, like she is asking us every night. But then my 5 year old son would also want to sleep with us and this is not practical or possible to have them both in bed. We allow them to sleep with us on the weekends. They take turns but it's always a reason for struggle and discussion. How would you handle that?