The major question is this: What types of pepper sprays, mace, or any other kind of spray deterrents, if any, are aerosol/flammable and would they be available at all?
And the details for the story are thus: The girl is seventeen. The story is set in early 2005 in the United States. Her father is the chief of police, and gives it to her to protect herself early in the story. The spray would be ignited with a butane lighter (probably a Zippo), held in front of the nozzle of the pepper spray—an impromptu flamethrower.
We’ve done all sorts of search phrases in Google—“pepper spray flammability”, “pepper spray inflammability”, “types of pepper spray”, “pepper spray legality”—and have also pored over every site related to law, pepper spray itself, and weapons’/self-defense legality we can find. The information that we’ve gathered, however, is often conflicted, or just doesn’t say at all. We really need to be sure, however, as it’s part of a major plot point.
If I have left out any specific piece of information that may help get this question answered, I apologize and will rectify the error immediately.
ETA: Edited because of missing information (if editing the post is illegal, feel free to mod-slap me); the state this is set is Washington State.