No, she obviously knew Muir was there so she did it. And that's fine - it's called racing. Have you ever raced? The space was free and she moved in to it. No foul committed. Nowhere does it say she has to run along the rail through the finish.
Not true. She was obstructed by Hissan and obstruction is against the rules. If Muir had just run into her, then Hassan's foul would have been obvious but that might have cost Muir a medal herself.
IAAF rule book says:IAAF Rule 163. 2.b. If an athlete is jostled or obstructed during an event so as to impede his progress, then if another athlete is found by the Referee to be responsible for the jostling or obstruction, such athlete (or his team) shall be liable to disqualification from that event.