As redcrx said has she alwars done this? can you think of a trigger that started it?
Consistency is the thing, Have a picture check list before she goes to bed, wee,juice,teeth, whatever you do etc, then you can show her you have done everything. When she wakes you are right to be firm and keep taking her back(providing she is obviously not ill or something) The first time you can show her the check list and she should realize it is tuff luck. You may have to keep putting her back but try not to say too much to her after the first time then she isnt getting the attention. Does she have a nappy at night? Maybe she needs potty in the room so she can have a wee and go back to bed.
Sorry but clear and consistent and you should make it. Sleepless nights come as a mega shock once you think they have gone dont they. Good luck xxxxx