My 21/2 year old daughter (ironically a twin as well) isn't a great sleeper either. She goes through phases, like your daughter, where she will sleep great and then will be waking at night for unknown reasons. I, like you, don't always rush in but I know the difference between the tired cry and the cry of "I'm having a tough time sleeping" cry. I often wonder if my daughter has bad dreams sometimes, because she'll wake up crying for reasons I can't figure out. Other times, I can tell she just is having a rough nights sleep.... tossing and turning, restlessness, and can't fall back asleep. Even as adults we all have occasional nights like these! I don't have any advice to stop your daughter from waking up at night, but the attitude I try to take (and I know its tough not to get frustrated because interupted sleep stinks!) is "she's just having a bad night of sleep". As far as the wet diapers, I limit the amount of liquids my kids have after dinner. A little bit of water is fine if they are thirsty, but we don't do cups of milk (for example) during story time before bed. You will notice a huge difference in their diapers in the morning and you will also appreciate this new routine once potty training begins! Best wishes and hang in there!