Prevent her.

You want to see this thief face justice. Preferably without any pants on, so justice can have a good long look at her pussy. You filch the knife from her fingers and stand back to watch the fun from a concealed location.

Soon enough the noblemen have sorted their argument out, and Lorenzo waddles off to fetch the guards while the other nobleman stays with the half-naked thief. He has a firm grip on her upper arm and he isn't letting her go anywhere, no matter how much she struggles. The guards, a beautiful tall blonde woman and a handsome muscular brunette man, duly arrive, both clad in their polished armour. The thief sees them coming and blushes, crossing her legs. The male guard raises an eyebrow at her predicament, but doesn't comment, though he glares at the noblemen. The female guard doesn't even flinch - she's probably seen plenty of shit.

They take her by the arms and tell her they're going to drag her off to the stocks. Justice moves swiftly. You watch from your hiding place as they walk her in the direction of a public square, and the thief manages to get just enough freedom of movement from them to at least hoist her pants back up to her thighs.