K.B.
The thing is, you cannot "train" them for night - it's just something that their body has to develop and they don't have a whole lot of control over it. There is a hormone that our bodies produce that naturally causes us to concentrate our urine more at night, so we are not having to go pee every couple of hours. But very small kids don't have this hormone yet, and when it kicks in varies from child to child. My cousin's daughter was still in pull-ups at night at 5 years old and even until 8, still sometimes wet the bed at night. She really couldn't help it. She also has a relatively small bladder so she naturally has to go more often, even during the day.
Realizing that you don't have any control over this hopefully will help you all to stop stressing over this any longer, and know that it will happen when it happens. Keep your daughter in pull-ups until she is waking up dry in the morning consistently and let her know it's okay, everyone gets there eventually and she will too - it's nothing she can help right now and she doesn't need to be living up to anyone's expectations when she doesn't have any control over it anyway. Her preschool teacher shouldn't care what is happening at night as long as she is in underpants during the day and able to manage at school. Right now still wetting at night is totally normal. No reason for your little girl to feel bad or ashamed about it.