Wow, you have tried all the best ideas already!
Here's an idea maybe to try -- put all the steps of her bedtime routine on scraps of paper (illustrated would be best), and ask her to put them in order. Include "Scream and cry," "go to sleep on the floor," "go to sleep in my cozy bed," as well as "Mommy sings me a song," "Daddy reads me a story," "I read to myself for a few minutes," or a few other ideas to include in a bedtime routine. Have her compose the way it should be. I think at 4 she is just trying to take control of how things should go.
Another couple of ideas -- it's impossible to make a child go to sleep, but we can discipline them for getting out of bed. When I transitioned my kids from the crib, they had such a hard time with their new freedom and couldn't learn to stay put! I had to tell them I would take their pillow away for a few seconds if they were not ready to use it. And I did, and they cried for 10 seconds, and then I gave their pillows back and told them I loved them and I knew they would do a good job learning the rule about staying in bed. This method is especially effective after buying new sheets or a new pillowcase. Oh, and if YOU pretend to want to be in that bed -- just lie down in it and say loudly how cozy and beautiful it is, and how it makes you feel sleepy and you don't feel like sharing it, that really helps.
Another idea is to stay just outside the door and sing, read a story, or count. Sometimes kids just have a bit of separation anxiety all of a sudden. For a few months when bedtime was especially hard, I would sit outside the door and count out loud, just to be soothing. I would count to 300! But counting that high guaranteed that my girls were asleep by the end. Or I would read a chapter book, just outside the door. Singing lullabies also helped -- I used to sing them myself, just standing outside the door, but now we have a CD. I think singing them myself was maybe more effective, but the lullabies on CD work pretty good too.
Oh, one other thing, sometimes it helps to do the bedtime routine during the day, just for play and practice. Have your kid pretend to sleep for a minute or two, and say, "good morning!" and practice again.
Isn't it weird how some kids go to sleep at night without troubles? Oh well, keep at it, and good luck!