??!?
Why in the world would we ever have seen or heard of it before that moment?
It's an Odin thing, and Harry actually knows very little about Odin's specific rules & dealings.
We're regularly learning new stuff about the Dresdenverse... Harry's early magical education (by Justin) was abominable, and (later) Eb was trying to teach something more fundamental than reams of per-mythology Elder-Lore, so Eb didn't add very much of this (outside of the White Council fundamentals, mostly amounting to "how interact with the Council and not get Damocles-chopped by Warden Snicker-snack").
Yeah, and therefore it came out of nowhere and somehow now needs to be accepted as absolutely ironclad canon? For me, the whole deal of making Murphy an Einherjar is suspect from the outset, since she was a devout catholic and that did not change by the time of her death. So a "yep, we took her and now you can't see her" from the norse faction seems just a tad sus to me.
What is the direct quote?
I'll extend the quote a bit to make it easier to find. But I posted it a few posts ago.

"You look pensive" Murphy said. We walked down an empty hospital corridor toward the Cook County Morgue. We'd have to go the long way around so that I could avoid any areas with important medical equipment. My leather duster whispered around my legs as I walked. My blasting rod thumped against my leg rhythmically, where I'd tied it to the inside of the duster. I'd traded in my slacks for blue jeans and my dress shoes for hiking boots.
Murphy didn't look like a monster-hunting Valkyrie. She was five nothing, a hundred and nothing, and was built like an athlete, all springy muscle. Her blond hair hung down over her blue eyes, and it was cut close in back. She wore nicer clothes than usual - a maroon blouse with a grey pantsuit - and she had on more makeup than was her habit. She looked every inch the professional businesswoman.
That said, Murphy was a monster-hunting Valkyrie. She was the only person I'd ever heard of who killed one with a chain-saw. "
Sorry but that doesn't make sense, because if it a direct quote from Harry, it wouldn't begin as you wrote it. Also killing one monster neither makes her a hunter of them, since it was attacking Harry at the time in the Lowes plant department and she happened to be there, and she surmised that a chain saw was the best way to kill a plant beast.
Well, I just quoted the section from the start of chapter five and Harry calls her a monster-hunting Valkyrie
twice. ^^
Could be that they are, but that doesn't change that Odin is a god in his own right and has his own set of rules reguarding the warriors he has brought to Vallalha.
Yeah, but you'd think that God is a step above him and frown on that. Since it's metaphysical stuff of the souls kind, I think the whole hands-off approach Uriel normally takes would apply here. But we'll see.
Michael is different from Murphy, he has never broken the rules regarding the Swords or being a Holy Knight. Michael doesn't have that kind of arrogance, Murphy openly displayed it believing she knew and could apply human law to Nic rather than God's Law.
"God's Law" is also a bit indeterminate here. He had no problem smiting all the vampires, but every time Nic plays the "Yup, I'm totally giving up here, teehee" card, everybody wielding one of the swords needs to take some stupid pills? In any case, even if Murphy erred in this particular instance, that doesn't just invalidate what she did at Chitzen Itza and that she was used as a direct conduit to deliver a message. In my eyes, that means the G-man owes her one.