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.