If nothing else, Grandma may have genuinely useful information about the nature of kades; even if it's only that she wasn't conscious while in there. If she was conscious while in there, she ought to be debriefed in detail, with Onni taking notes.
But it's the emotional stuff that's really missing. Is she glad to be rescued? Does she feel like she was rescued? Is she, and is Tuuri, resigned to going with the Swan? looking forward to it? wishing there were some way out of it? The swan demands two souls; did Onni volunteer to be one so that Tuuri -- or Ensi for that matter, though Tuuri seems more likely -- could stay? if so, how did they react? Does Ensi have advice for Onni? encouragement? is she still angry at him? Did Ensi want to know what Onni and Tuuri's and Lalli's lives have been like since she left them? If not, why not?