Is she a pullet and is that her first egg? That happens all the time. By domesticating chickens we have messed up their natural seasonal rhythms. They lay a lot more than they used to when they were wild. They do not go broody as often. You probably feed them pretty well, their food supply doesn't drop in the fall/winter like it used to when they foraged for everything they eat.
It is a regular occurrence for some of my pullets to lay their first egg this time of the year. I also do nothing to enhance egg laying.
A few of my older hens have finished their molts and have resumed laying, so it's not that unusual. Feeding a higher ration feed can help them get through their molts quicker and resume sooner. Another few hens have just started molting, so everyone is different. Congratulations on the egg.