Hi H.,
I have been through the same thing, allthough my daughter was a bit younger and I was pregnant, so I needed her to stay in her bed until the baby arrived. A lot of mom's are probably disagreeing with this, but it really works, it did for us. The way it sounds you are already letting her scream and cry it out. Try this, when putting her to bed, go in after 3 min (if she's still crying) and tell her with a calm but assuring voice that you are still there and that she needs to go to sleep and leave the room again (you can spend up to 2 min in her room), increase the time to 5 min and then go back in and do the same thing, then 7 min, and after that 10 min., should she still be screaming after that, go in every 10 mins. It is not easy I know, my daughter even vomitted a few times, which made it even harder, but my pediatrician told me that this is ok. It will probably take up to 3-5 nights, but after that it should be a piece of cake. This is my secret, worked for me with both of my kids. I wouldn't switch her too a "big girl" bed just yet, in my opinion that would be too many changes in such short time. I would work on the going to bed part first before switching her into a new bed. Good Luck. Feel free to contact my if you have any questions or should you try it, to let me know how it worked.
Best wishes,
Trisha