[Co-parenting] What do I say/do when my daughter constantly demands her mother (ex-wife to me) when it is time to go to sleep? (and thus, won't sleep)

I am unsure how to actually handle this situation or what to say and looking for examples of what to do and not actually calling her mother and getting her to come and pick her up.Until my daughter was 3 and a half, I had always been there as an involved and active father. Her mother and I separated when she was 3. At 3 and a half (during which she was regularly staying with me) I allowed her mother to take my daughter overseas for a year and I had said I would also move, 4 months into that year (as I had research to complete), to be there for my daughter (who is almost 4 now).Now that I am here, I have been slowly spending more time with my daughter (as I had only had skype contact for those 4 months) with the aim of going 50/50 shared care and we are now in the phase of having her stay overnight (first night tonight).However, when I try to get her to go to sleep, she becomes very difficult and constantly demands "I want mommy" and insistently repeats that over and over. I find it very difficult to deal with and am unsure as to how to respond. It is additionally difficult because her mother is also quite manipulative and has used the fact that my daughter makes these demands (wants mummy to come pick her up) and that my trying to pacify the situation to get her to settle down and eventually sleep, implying that I am mistreating my daughter. As though, the non-mistreating thing to do would be to return her to her mother that evening. But that also means it will be highly unlikely for me to actually get my daughter to be fine with staying over and not incessantly demand her mother/to be returned to her mother if, every time she demands it, I return her.She is absolutely fine with me in all other aspects and additionally demands to come with me or stay with me on multiple occasions that I've dropped her off to her mother. So there is no issue with our bond in that regard, it is just that the bed-time routine becomes a demand for her mother, whatever it is they do (I suspect her mother lies in bed with her until she sleeps).Any advice would be greatly appreciated. via /r/Parenting https://ift.tt/2Oiy22X