they offer a bitter comfort that is so much more than anyone else is willing to give
and
Would she care if Angelus were let loose once again? That’s the thought that frightens her
Those two things bring back that sense of desperation and depondency that made everyone hurt so badly for Willow in s4. That made everyone feel her pain as if it were their own. (And made some of us wish that ME had made better use of Spike in s4. LOL)
I think you did a wonderful job here of explaining the utter emptines Willow felt during that time, and why her actions (or lack of them) in these pieces are completely understandable.