You can't prevent the new Maid Mareian egg from going directly to a nest because when Guinedeer hatches, that nest is empty & the Mareian egg goes there. I could only watched the animation as the egg zipped onto that nest.
(As mention earlier, we do not need to breed King Barkthur + Guinedeer to get Maid Mareian, that task is already marked as completed even before Guinedeer egg is put to a nest.)