Good point that it suggests there was rather than currently is an active nunh. And yes, I was thinking of R'ashaht Rhiki as a 'confirmation' that R'rhiki Nunh seems to be a proper character and not a random name they've put together for example. (They could be full sisters, I guess, although R'ashaht's lorebook profile doesn't mention any - but does mention her leaving "her parent's home" which is either poor grammar and a sign that they're not in a full tribe situation, or a quiet nod that she only has one 'parent'. Or a lore/translation error. To the lorebook bug thread!)
There are a few other character names I recognise scattered through the page (U'odh Nunh, Alka Zolka, Silent Moss) - perhaps those were by chance, though Merlwyb Bloefhiswyn is specifically used as an example breakdown of Roegadyn name patterns. So between R'sushmo being an actual NPC and her name adding up with the one other R-tribe character we know the full name of, it seemed likely to be canon.