She has a reason. she's scared. I used to suffer from horrible nightmares and I ALWAYS found my way into either my mother's room or one of my brothers up until I was probably about 11 years old.
If she really needs that comfort, I'd let her have it and hope she'll outgrow it soon. I wouldn't let her sleep in my bed, but I would tell her if she was scared, she could bring a blanket and pillow into my room and sleep on the floor.
If I was totally against that, I'd sit in her room and read til she fell asleep. But if she woke in the middle of the night scared, I'd let her in my room (on the floor).