I had to doodle this, sorry.
Oh, my heart! *immediately swoons*
And I was making up even
more headcanons on this while I was walking back from work (see,
this is what I do when I don't have a book/can't read a book/don't feel like reading a book). So after the Second War, Headmistress McGonagall kept looking for a new DADA teacher, but ever since Voldemort cursed the job they'd already gone through pretty much everyone who'd even
think about taking it, so they had a short run of a few mediocre teachers who hadn't lasted more than a few years each.
Then, out of absolutely nowhere, in walks this Norwegian exchange student who'd graduated a few years back, says she's gotten bored trying to work with the giants and that she wants the job. McGonagall has a long memory, and she remembers being extremely exasperated with her throughout pretty much her entire time at Hogwarts - she flunked Potions, didn't even try to hide the fact that she was skipping History of Magic, and spent pretty much the entirety of every class that wasn't Defense or Care of Magical Creatures mostly just goofing off. But McGonagall also has a secret soft spot for her that she is never,
ever going to tell anyone about, because she could tell this Eide girl was an innately talented witch (if only she'd put in a bit of effort!), and the number of Quidditch matches she helped win during her time on the team, even more after she'd made Gryffindor Captain, certainly didn't hurt. Plus she's the protege of a famous Norwegian wizard who helped them out a lot in both the first
and the second war against Voldemort, her parents are both extremely talented Norwegian Aurors (or whatever it is they call them over there), and she's been personally dealing with giants for the past few years; she certainly isn't lacking in hands-on experience.
So, McGonagall figures that at the very least it can't hurt to give her a shot, the last few teachers they've had certainly haven't been prize material and they can't afford to be choosy, and Sigrun just. effortlessly blows through everything they throw at her and keeps asking when the warm-up is going to be over so she can get started on the fun stuff. Finally McGonagall just gives an exasperated sigh and hires her on the spot - but only after making her
promise that all of her students are going to come out of her class alive, thank you, and with no permanent injuries.