Something like these blankets could be helpful!
Especially if your daughter could have some of the issues that others have mentioned.
(If it is an actual 'sleep-issue' then, maybe not so much. She might just toss and turn and the thing ends up on the floor.
You don't have to answer here, of course... but if you were to guess... which way do you think it would go?
I might try to come up with something before actually buying one of these blankets...
Most bedding now is made to be lightweight. But, especially with Winter coming, maybe you can find a type of blanket that is heavier, just double it over... and that would have enough weight to help.
When my son was little, I would sometimes find him 'Cacooned'.... (yes, this is an actual medical diagnostic term...) wrapping himself tightly in blankets or even a winter jacket, using it like a sleeping bag.
I used to stop by his room before I finally went to bed for the night, and adjust things, so he wouldn't overheat or suffocate!!!!
I do agree that at her age, it is time to take whatever steps necessary to find out what it will take for her to sleep at night, in her own bed.
Sending best wishes...
I know it must not be easy. I would HAVE to do something, because I NEED MY SLEEP!!!