Sleeping problems with 16 month old daughter ... how can I prevent her from waking up and not?

Hi, what kind of milk is she having? I think she is thirsty. My son is 15 months and give him the but it is only to go to sleep now and first thing in the morning as we are weening him off. But I find if he has a full bottle of formula he sleeps all night. My son is going to bed around the same time as your bub, he wakes about 6:30 to 7. I find the formula fills his tummy for much longer so he sleep more sound. May be you could try it, it may help. If she continues to wake up at midnight try sneaking a bottle of formula into her mouth around 11 it couldn't hurt to try. That's all I can think of don't forget she is still a baby and good luck with the sleeping.