All these people calling her dumb are only able to do so because they have reader omniscience. If the panther didn't have this trump card handy, he'd be wrapped up nice and neat, and be a useful bargaining chip just like she planned and none of you could have said shit.
She can't see the future. She made a good plan and carried it out, but was interrupted by a thing she couldn't have prepared for. You can't call someone dumb for that unless you're dumb yourself.