I'm working on a character for a Reign of Winter game that's going to play on the Paizo boards, and my character is an Agathion-Blooded Arctic Druid. Andyla's campaign trait is Warded Against Witchery, and I was reminded to remember that the game starts in Taldor in midsummer, so I should have a good reason for being an Arctic Druid in Heldren.
Well, my background concept is that Andyla's adoptive father is an Ulfen from the Lands of the Linnorm Kings, who had married a Taldan woman from Heldren. When Andyla was a baby, she was mysteriously given to her father by a mysterious woman soon after his wife had died. Sometime recently in her life, Andyla relocated to Heldren, the home of her father's wife.
For the Warded Against Witchery trait, I'm thinking she perhaps had a run-in with one of the evil dolls in the huts at the borders of Irrisen.
As a warden of winter (essentially) it's easy to argue that your character would be attracted to Heldren after hearing news of the supernatural cold in the Border Woods. Unnatural winter might piss your character off, as it's essentially your domain and causing something that unnatural on such a large scale is seriously whack, yo.
As for running into something winter witch-ey you can say that she had a run-in with something in the north that did some serious damage to her psyche. A doll hut is a good choice, and that encounter could have been a wake-up call that despite her heritage she isn't ready to take on the unnatural blight that is Irrisen.