It was a small detachment of hobgoblins who were low on supplies and trying to catch up to their main force. They needed food and the village had it. And hobgoblins aren't particularly ones for asking. They raided the small village late one night, killing everyone they could find and burning down whatever they couldn't take with them. Scarlet hid in a crawlspace under a house as her village was slaughtered and fire fell all around her. The heat slowly burned her, but she was too afraid to leave her hiding space. Eventually the hobgoblins went on their merry way and Scarlet emerged from her hiding space, weak and charred.
She likely would have died there were it not for some wandering adventurers who pitied her and healed her wounds on their way back from clearing out a warren of goblins. They took care of her for a short period, but the adventuring life is no life for a small girl so they soon left her in the care of a nearby village. She became obsessed with death and soon apprenticed with a local Suomi priest and learned the ways of funeral rites. The priest taught her how to make death masks and while she wasn't particularly excellent at it, she did good enough work.
Now after such a traumatic experience with fire, it is reasonable to assume that she might not exactly be fond of fire. However, that could not be further from the truth. In fact, Scarlet became obsessed with fire, believing it to have been the one thing that saved her from the blade of a hobgoblin. She constantly played with fire and became an accomplished fire breather. Eventually she saved up some money and was also given some by the other villagers. She used that money to train herself in the arts of fire magic. With her first studies done, she returned to her adopted mountain home, and used her magics to perform last rights for the dead, creating fantastic funeral pyres which were both terrifying and enchanting. The local villagers were a little uncomfortable with her obsession with fire (since their homes are so flammable after all), and eventually Scarlet chose to take to the road, joining up with a couple of wandering priests.
It was a few years after that that they were ambushed by lizardmen. One of the priests died in the battle while another was captured. Scarlet used her magic to vanish from sight and followed the group to the lair of a witch. Scarlet prepared her plans to rescue her friend, but before she could do anything, he had already been freed...