Meeting the Dragon Riders
Chilblain sends iron ore to Berk and other locations very punctually, however, Gobber notices of late, they have not received any at all. Concerned, some of the Hairy Hooligan Tribe and the Dragon Riders sail to chilly Chilblain to find out about the lack of deliveries. They find that the village is in chaos from the arrival of Dragons and the eruption of Mount Ymir.
While the adults meet and discuss their predicament, the Dragon Riders meet with three Chilblain kids named Kettil, Frey, and Gunilla. Unlike the adults, the children are interested in Dragons and Dragon riding. They teach Hiccup and the other Riders about a game they play called "Snowmageddon", which involves a snowball fight while "surfing" on sleds across the snow.
At one point during the game, Gunilla appears to have won "Snowmageddon", but as she is announcing her victory, an avalanche falls toward her. Hiccup sleds to the rescue and whisks her out of harm's way.
Training a Dragon
Unlike Kettil, Gunilla is not seen taking a crash-course in dragon-training. It is not clear she even does train and ride a dragon. However, one comic panel shows a distant rider on a Gronckle exclaiming "We're ... flying!", which is not Kettil or Frey, and not a Dragon Rider. This image bears a resemblance to Kettil, however he is seen elsewhere on the same panel on a Dragon. It is possible this was intended to be Gunilla.
Gunilla is a thin girl that appears to be about the same age as Hiccup in the Dragons: Defenders of Berk series. She is about the height of Astrid. She wears brown pants, a purple tunic, and some sort of reddish-brown wrap. She has shoulder pauldrons of possibly leather. Gunilla has long, waist-length red hair with a grey headband.