I'm not much of a gamer, but I like plots and developing things. Looking at what you've provided, I see a couple possible plots. But I'm not sure how "playable" they are.
What might help is to know why she feels the need to send out this warning? Are others threatening her territory? Is she under pressure from Wamps or someone else?
As for the secret agenda, here's what pops off the top of my head.
1) While seemingly random, the targeted locations are those contested by this other organization. Fairly obvious, assuming the players know the area. If not, then they have to figure out why, which leads to who.
2) Their attacks aren't just to show power, but to garner a specific response. By taxing official resources to respond, she could be advancing an agenda to provide contacted services to the city. Just like there are private EMT services, she could be advocating private fire and police services, which she would control.
3) The attacks are seemingly random, but are actually devaluing land and property in strategic areas. The attacks are a cover for a land grab, which would help her and the Ramps expand their control in the area.
The one with the most action potential, as it implies she has forces in place to act as police that can be fight. A combination of all three plots might be best. #1 is the known plot in the supernatural community, but the players aren't sure why other locations not associated with the Ramps enemies are being hit as well (#3). And then the shoe begins to drop as the first responders that arrive are her people (#2).