The only difference was that Milo knew what he was doing, using civilians as tools for his amusement, whereas that wicked wolf was oblivious. She believed she was doing the right thing but ignored subsequent construction and development, cared nothing for future stability and livelihoods, and engaged in so-called "salvation" driven by her own sense of justice.
In the end, it was just about satisfying her inner desire for righteousness.
Considering Fenrir's various circumstances, as the person leading the preparatory work for this operation, Boneblade would rather take the reckless route of diverting the Whistling Legion's attention than attempt to communicate with Fenrir.
As for that unknown adventurer, they speculated that the individual was probably an enemy of the Whistling Legion, likely seeking to stir up trouble just like them.