I could have written your post, uncertain!
I had a couple of threads here & on the sleep board because about a month or so ago I was at my wits end with DS's inability to stay in bed.
We are definitely still in the thick of it & so I have no true answers to your question... just commiseration.
We have tried what a couple of mamas suggested to me -- letting go & letting DS set his own bedtime. Most nights, we go through our bedtime routine as early as we can manage & then leave him with a reading light on & his books. He will sometimes turn of the light himself & go to sleep, sometimes within 40 minutes but more often it's an hour or more.
In fact, we're just sort of going through the process of reevaluating the current system because I am really thinking that he is not getting enough sleep (plus after a trip he was back in bed with us for a week & now wants someone to lay down with him in his room).
So we haven't hit on one thing that is working consistently yet.
BUT letting him read to himself (& by read I mean flip through his favorite books) has given me the space & time I need to let go of anger & resentment that was building up previously. I still have nights where I can muster more patience than others, so I too am still a work in progress.
Bedtime is so, so, so hard. I can almost deal with anything my son throws my way at any other time of day, but at night I just can't do it. It is so frustrating when he comes out of his room within seconds of me tucking him in for the 30th time! I can't even brush my teeth some nights!
But I realize that it's also my job to listen to him & really figure out what he needs to settle down for the night. Like your DD, my son is often half-asleep right before we actually get him in bed & then wakes up & won't settle.
I think it could be the age. Fears can be really clear & strong right now (from my limited observations) & DS's ped. just confirmed that they can go through another attachment phase right around 3. Is your DD new to her own bed/bedroom?
I tried just talking to DS one night as I lay with him to help him unpack his day & that seemed to help marginally.