I personally would persevere with having your daughter for overnights a little longer and try to change the routine you may have to see if other things you could do may help, they may not but would be worth a try.
You mention watching a film before bedtime. I think this is both an isolating pastime in that communication is not taking place between the two of you for that period and films can also be too stimulating prior to bedtime.
One or two biscuits at the most and an appropriate amount of milk just before bed may help.
I think it induces sleep in a child if their bed is warmed before they get in it.
Having their favourite soft toy to cuddle may be helpful and comforting to her.
Have you tried reading a happy soothing story to her when she is in bed in a quiet voice with the light dimmed (no fairy lights) or the bathroom light left on and her bedroom door left open? Encourage her to close her eyes and listen to the story.
Classical music is not to every persons liking but a portable radio on the floor, tuned to Classic F.M. with the volume turned very low indeed can be soothing and provide company i.e. a diversion.