"by finger--painting with dog poop?"
No, from revenge. I didn't expect her to rub the feces in, but I should say she had gloves on and used the plastic bag too. Gross, but it gave her a sense of power over a man who took it from her.
Is this not a judgement on your part? Unless there is something I'm missing from your narrative, the english translation of what happened is your friend got offended at being man-handled and did an obscene amount of damaged in revenge.
It would seem to me even though you call yourself followerofchrist, you still give some approval to the action because you are choosing to rename the act in terms that blame the victim of your vandalism.