I just had a thought, and now I have to listen to this one again…
What if the little girl was a robot -- the robot embodiment of the land's protector? That would explain why she was so passively involved in relationships, why she had little concern for what the troll would do to her, and how the Dala horse crawled into her head (maybe it didn't actually crawl in, but it was some sort of threat assent module that, when plugged in like a thumb drive could activate the defenses).
For that matter, the whole thing could be a virtual world metaphor inside software… The girl is the defender program, sent out to waylay the troll virus, which turned out to actually be a Trojan to get the bigger baddie into the system, but the defender program actually had a Power Rangers-esque upgrade card at her disposal -- the Dala horse -- and used it to squash the hacker/big/virus/whatever.
Maybe it's nothing, but re-listening with either of those in mind might make me dig the story even more.