Have you been taking temperature or anything? When did it drop? There are usually pups much sooner of the drop (2 to 12 hours) but if there aren't any within 24 hours of that you would want to call your vet.
There would be no way to tell how long by when she is nesting. She may nest just before she may nest days before or weeks or she may not nest at all. They are all individual in their behaviors though that is a fairly common sign. There is more information and links on breeding and whelping in the link below for you (procedure, danger signs, normal and not normal, what you need ect.).
q3525724.html#a2810229
q5762034.html#a2906893
There would be no way to tell how long by when she is nesting. She may nest just before she may nest days before or weeks or she may not nest at all. They are all individual in their behaviors though that is a fairly common sign. There is more information and links on breeding and whelping in the link below for you (procedure, danger signs, normal and not normal, what you need ect.).
q3525724.html#a2810229
q5762034.html#a2906893