Good discussion, but I haven't heard much about why the Brazilian authorities arrested the US marshals. Why would they believe the woman, and not the marshals? Did the captain or other crewmembers back up the mashals' story?
Regardless of what happened on the airplane, the Brazilian authorities should have listened to the marshals' story, taken custody of the woman, and dispose of the situation from there as they saw fit - either released her and then have the marshals submit a written statement, or other similar action. Ask the marshals to be available for testimony during any investigation, etc...
For the Brazilian authorities to arrest the US marshals on the spot, at the airport, to me doesn't fit the situation.