B.W.
All kids are different too you have to remember that. My oldest was potty trained at 22 months and immediatly was dry at night too, never had an accident. My youngest has been trained since about 16 months and is now 22 months and still wears his cloth diapers at bedtime, he is just that sound of a sleeper. Though he's not nearly as wet in the morning as he was, I get him up and take him, he still has his diapers slightly wet in the morning.
Each child is different and I do think that night training isn't even close to the same as day training. Try cloth diapers, maybe the sensation of being wet would help her wake up and learn to get up to pee at night.