C.F.
Does she have all of her teeth in? Molars too? They usually come in around 24 months, but can certainly come earlier (my daughter had all of her teeth in by 15 1/2 months). If she is in some discomfort, that could wake her up. You may want to try giving her some tylenol or ibuprofen right before bed. She could also have an earache or ear infection that is causing her some pain as well- tylenol would help her with the pain, but she would need to get on some antibiotics, too. It could be a growth spurt. Oftentimes when kids are growing, they either sleep a lot more or have their sleep patterns interrupted. Is she drinking a lot of fluid in the evening that is making her have more wet diapers? These are the only things I can think of since you said she doesn't seem sick. I hope you can solve the mystery and get some sleep! Best wishes.