maybe she is thirsty?
you could try giving her a dream feed of water just before you go to bed and see if it works. my lo went through a similar stage. since i was still dream feeding her properly, I just watered down her formula in order to get a bit more liquid in her. seems to have worked and she now goes through until about 8-9!
I've even found that if I am going out in the morning and will ruin her morning nap, i can dream feed just before 8 and she will sleep until about 10! Fantastic method Tracey has there - I don't know how we would hav coped without it.
anyway, don't know if this will help, but give it a shot if you want
Jenni