I think it's fairly clear that this fire was not intended to spread and had little chance of spreading.
To be clear, I'm not saying what she did was right--but I am saying that if we look at intentions and what was likely to happen, this clearly was not done with the intent of destroying anything but property.
And to be clear, if you look at the George Floyd murder and protests, and your biggest concern is the torching of two unoccupied police cars, you aren't concerned about justice or public safety.
I'm sure that wasn't her intention, but serious fires are started by people who didn't intend to do anything more than have a campfire or fireplace. It's reckless, and it's counter-productive, turning people against the protests.
And just to be clear, it's entirely possible to be concerned about both police brutality and arson.
Well, first of all, "police brutality" is not the worst problem or the problem that incited these protests. Police murder is.
Second, if you're concerned about both of these things, then there's no reason to talk about putting protestors in jail. She didn't set fire to a police car because she didn't know there might be consequences. She set fire to a police car because those consequences don't matter to her. If you care about both police murder and arson, then you should be talking about stopping police murder, because that's the cause of the arson.
Focusing on the violent components of the protests is part of a strategy that controls the narrative. At every turn, kneeling on a man's neck for 8 minutes and 46 seconds while he begs for his life and slowly dies is being downplayed--calling it "police brutality"--the same term used for slamming someone against a cop car while you handcuff them. And at every turn, things like burning a police car are being played up, calling it arson--the same term used for torching a city block with children inside. And in fact, people in this thread won't even call it arson when Philly PD actually did torch 61 homes, killing 5 children[1]. Where are the people insisting that we call that arson and bring the perpetrators to justice?
So yeah, it's possible to be concerned about both police brutality and arson, but "police brutality and arson" is not what's happening. "A police officer murdering a man and a woman setting fire to two unoccupied, isolated police cars" is a much more proportional description of the events. And if your main concern here is making sure that the woman who lit the police cars on fire is brought to justice, you aren't proportionally concerned about both these things.