HUGS to the sleep-deprived mum!
In our experience with DD, she is a pretty easy kid, but will take anything and make the most of it when it comes to bed/nap time routines. She sleeps through the night for the most part, but if she wakes up with a runny nose or some such one night, you can guarantee she will wake up the next one or two nights and try it on!
I would still say we need to 're-train' often, and shut down night wakings as quickly as we can!
As for the screaming, did she have a bad dream/nightmare?