You mean the costs of their overreaction? Why should she have to pay when the Boston police (once again) overreact and act hysterical?
No, the fairest solution would be for the police to let her go with a warning. The warning should be something like this:
"We the police are too stupid to think like adults and we think blinky lights are scary and they make us want to pull out our machine guns. We've done it twice in the last six months and we'll probably do it again. So consider this your warning. No more blinky lights around Boston police, okay?"