DD is 21 months and has been put in her cot for sleep but for the past 40 minutes has been screaming "need to get out", "need some orange juice", "need to get out", "please mummy". There's no sign of it stopping. She's never been like this before but for the last few nights she's been a nightmare. I've been talking to her over the intercom thing but am reticent to go into her for fear of setting a precedent. There's nothing physically wrong, she just doesn't want to go to sleep and wants attention and has got herslf into a right state.I don't know what to do for the best. Any advice?