5yr old will not stay in bed. At wits end

[feekerry]

Posted a version of this in behaviour but things have escalated so posting for more ideas
My dd is nearly 5 and out of the blue has started not wanting to go to bed, and then also getting out of bed constantly thru the night coming in to our bed. At first I kept putting her back but this has now escalated to her having an absolute screaming tantrum every time I try putting her back inc making herself sick. She literally gets out as soon as I put her back. She shares a room with 3 yr old ds so I don't want her to wake him up which she does if she starts screaming and he becomes frightened.
She has also become very anxious in the day and I presume the 2 are related but there has been no obvious trigger. This has been about 6 weeks now. Have been to school ( all good there) health visitors (all suggestions failed) and tried every method etc I can think of. She literally won't stay in bed.
The times she has come in to our bed dh has to sleep in living room as she wriggles and kicks all night and has to share my pillow. It's just miserable.
What can I do. Some nights I battle with her from 2/3am and no one ends up going to sleep. She won't even sleep on a mattress on our floor. It has to be in her bed and her head has to be on my pillow. It's becoming unbearable.
She says anything from she misses me to had a bad dream etc but it's constant. She doesn't even fall asleep quickly in our bed. She faffs, genuinely doesn't seem that tired.
In desperation I have tried holding her door shut so she can't get out but she almost kicked the door in.
The more sympathetic I am in the day the worse she is at night.
How the hell do we deal with this? It's so hard to be positive and affectionate towards her when she has had everyone up all night