Most Wellsummer are not great layers, they are bred mostly for egg color, they start later and are sporadic layers, stopping and starting through the season, most laying age pullets will start a month or so later this time of year as opposed to one beginning earlier in the year due to the temperature changes and the decreasing light, I haven't found providing extra light for first season layers to do much, she should start in the next month or so, make sure she's still on a non medicated grower or an all flock that has higher protein so she has enough to continue growing and maturing as well as firing up the egg laying machinery.
Your Welsummer has had the misfortune of hitting the right age for onset of laying at the same time the days got too short to provide the necessary hours of daylight to stimulate the egg laying hormones. I'm in the same boat with three pullets of my own who are the right age but the day length simply isn't cooperating. I'm certain they will begin laying as soon as the days begin adding length again, perhaps sometime after the new year.
I have five Welsummers who have been super layers for the three years they've been laying. They are molting so aren't laying currently, but they are all daily layers of enormous eggs of fine quality. I would never hesitate to recommend Welsummers to people who want ginormous brick red eggs and dependable layers.