My son went through a phase where he woke up an hour or so after going to sleep EVERY night.
I was lucky to receive this book, Healthy Sleep Habits, Happy Child, by Marc Weissbluth, MD.
There is a lot of information in the book, including medical and biological reasons for the way we sleep, why it's good, etc. But really, once you get into the sections with ages and routines and suggested ideas for good sleep, it's not quite such "deep" information. (I must say, I liked the stuff in the introduction, even though I didn't understand every single word of it!! I liked knowing the benefits of good sleep, etc.)
The thing that I first thought of when I read your post was that your daughter is just at the point where she's needing to learn to soothe herself back to sleep. There's a number of suggestions about the amount of crying you're willing to tolerate while you go through that process, in the book, and when I did it, I'll be honest, I just let my son cry. It was excruciating. Every minute crying seems like SO LONG!!! It was horrible. I doubted myself. But eventually, my wonderful little sleeper returned. Now, it's a joy to listen to him in his crib every night. He is SO CUTE when he's winding down for the night. He talks, he sings, it's precious!! He only cries very rarely, usually when something out of the routine is going on.
Good luck to you, you'll figure it out!!