how old is she? DS did this, seemed like forever, up to very recently. I wish I could give you a diffinitive reason for it changing, but, I would say it was time. I tried everything - Wake to Sleep, Shh-pat, pickup/put down. I even tried controlled crying. Eventually we brought him in with us at 4-5am and he learnt to go back to sleep. Now, he often sleeps through that, and sometimes he still comes up to us. He is 2.10 so now he can bring himself to us, rather than us having to get up to see to him, so although I wake up, it is not as traumatic as getting up to settle a crying boy. He tends to sleep 8pm-7am now, sometimes coming to us, and back to sleep, sometimes sleeping through.
I think/it seems that he started sleeping through properly once all his teeth where through. I am not sure/dont think that is the only reason he did not sleep through but it was a combination of a lot of things. And once he was ready, he still had tooth pain.
This time last year though, I was despairing as he used to wake at 4-5am for the morning, sometimes waking once at night too (18months ago, well, lets say, it was the toughest time for me as a parent, ever as he just refused to sleep for long).
So, while I cannot give you a magic cure, I can say that for us at least, it did end, although maybe not as quickly as you want to hear!