Be firm with her and be consistent, do not sit by her bed for her to go to sleep, let her read with a small light on and leave the light on if she wants to , but tell her that's her room and that's where she must sleep.If she comes to your room send her back, or take her back.She will get it after a few days , if you give in you are back to square one .The floor is winter is too cold so thats not a good idea. Be firm and it will work out .good luck
Have you ever thought of getting her a teddy bear, or another stuffed animal? When you give it to her you can say something like "This is ___(insert name here) and he/she has come to protect you from whatever you are scared of. "