I think it's interesting thta you identified the debris microscopically,
and now where is it coming from.
I have a biology degree, though not entomology, so I won't be of much help
here. However, if the question is how it got there, I would think, based on
my understanding of the layout and structure, that whatever infestation she
had or has is likely underneath the siding, and and chitin and other
materials
continue crumbling out. Has she tries hitting the clapboard with a fist (or
whatever) to check for this? I suspect the amber might actually be that,
considering the Cedar.
I looked for a suitable biology site for you, but haven't seen one yet.
I'm curious what others will say about your situation.

Les