This was probably meant as a piece of performance art or an "amusing" act of protest. In spite of Star Simpson's protestations that she'd only wanted to draw attention to herself on "Career Day," it seems more likely that her actions were meant to provoke exactly the kind of reaction they elicited. I'd guess she knew perfectly well that non-scientists/engineers would assume her device was explosive.

I agree with other commenters: No terrorist who actually knew how to build a real bomb would build one that looked just like one, then carry it around in public. But a nut with grievance might. Terrorism aside, we've seen bomb-building nuts before. The police might not have thought they saw a terrorist, but just a crazy woman with a rickety, but possibly dangerous explosive device.