J.B.
I would ask the pediatrician if she might have acid reflux. My baby never spit up but had it. When they are upright the reflux doesn't come up nearly as much, when laying down it comes up their throat a lot and then back down (so they don't have to throw up out of their mouth for acid reflux). If you are absolutly certain she does not have acid reflux or anything else wrong then the only way to break it that I know of is to leave her there and tell her, "mommy is here, mommy will get you in a bit, mommy has to do ______" and talk and explain to her what you are doing, etc. If she is so upset she isn't listening, don't worry about it. Talk quieter and it might peak her interest. But I wouldn't do this unless you are certain she isn't dealing with something like acid reflux (my baby was and acted the SAME way, once he got medicine he stopped).