That's the point.. SHE was not the Assassin. Right now it appears like she was fooled into applying the poison to the Target.
But in other reports it appears that Police are stretching the dragnet to other guys, as it seems like they have yet to "Exit the Map".
Talk about Professional Difficulty.
Reports also indicate the VX poison was split into two parts that "mixed within the Target once both are applied". The purpose clearly was so that the elements were not lethal to any of the Assassins but would be deadly "within the Target".