As far as I can tell from our Doyalist universe, Valkeries were essentially Odin's angels- supernatural/immortal/*spiritual* beings who took human form (attractive female human form), but who maintained their status as non-humans, and served two purposes (relevant to us)- main purpose as "choosers of the dead", selecting "worthy" heroes and transporting their spirits* to Odin's hall (or Frigga's), and providing *ahem* gratification to those spirits during nights of feasting and revelry.

*Said spirits appear to exist in such a fashion that they are essentially embodied- capable of interactions mimicking the physical in all ways.

My question is this- in universe, valkeries (such as Freydis and Sigrun) appear to be merely mortal (human or not) beings in human female form, but with their supernatural existence reduced to supernatural abilities- strength, speed, magic in the form of runes, in a mirror of wizards (mortal humans who have inherited similar powers).
Sigrun indicates that mortal heroes (such as Hendrickson and Murphy) cannot return to the *physical plane* until mortal memory of them is gone, but are the valkeries mortal for that purpose? Even assuming that Dresden and Marcone (and others who started out mortal) die (or no longer qualify as mortal for that purpose), is Sigrun really cut off from Nathan? Even if she has been around long enough to remove the musket ball from Nelson's body at Trafalgar, is she really restricted from returning to Odin's halls and seeing Nathan as an Einherjarin? For that matter, why shouldn't Freydis get her chance at Murphy?
How close is the history/legends of our readership to the in-universe history/backgrounds of the valkeries?