This dummy spitting thing is SO frustrating hey? My little one used to do the same thing. It sounds as if your daughter isn't quite ready for sleep or that there are other issues stopping her from being able to settle. I know when my 8 week old daughter does the dummy spit thing it means she will not settle and that i must try something else to get her to that point. For example if I put her down and she spits her dummy out every 5 minutes i would first try burping her again. Failing that i'd give her more to eat (and then burp again). If that doesn't work then i'd try changing her bottom and making sure she's not too cold or hot (you know all the usual things). Also sometimes i put the dummy in her mouth and she actually takes a while to get into a good sucking motion with it so if i gently hold it in her mouth and even tap on it for a while she eventually figures out that its there and latches on. When you put it in her mouth does she roll her eyes back or shut them or something like that?? How long has she had a dummy for? The only other thing i can suggest is perhaps a lighter weight dummy... One such as the "Happy Baby" dummy which is very light and easy for bubs to keep in their little mouths. Other than that she just might need more and more practise with it!
Good luck, i hope this helps you a little....
Sarah, mum of Natalie & Jessica