The things that cause birds to lay eggs are called Ova (translated: egg). All females hatch with ova inside them. Chickens have about 1000 ova, and Ducks about 1500. Ova are the most important element of her body's egg-making function, yet, there is no function to make more Ova, so when they've laid 1500 eggs, they will never lay aggain. This is why Red Sexlinks and Khaki campbell 'burn out'; they've been breed to use up most of the Ova in a very short time, and that is why a Runner will lay consistently for 2 yrs, and then lay lower numbers every year, and a Rouen can lay 25 eggs a year consistently for 10 yrs. And that's why egg ducks will lay for a longer time than egg chickens; they can make more eggs.
Is she molting or has the weather changed where you are? My runner girls stopped laying a couple of months ago when the weather was getting cooler. It would be cold one day and then hot again the next and threw them off. I am asuming that once the weather warms back up my girls will pick up again so I would go with weather.