Despite what you think,the fact is she wasn't level.
It was very harsh,and very unlucky,and i think such intervention takes humanity from the game.......but ultimately it was the correct decision.
We don't know it was, and that's the point, its a single frame used, who picks that frame ?
With players moving quickly, often in opposite directions, the ball moving quickly, there is still scope for error, because the technology is not up to the job, we don't even know that the lines we see are in perspective.
Not a single USA player appealed, until after the goal was scored, well they would then wouldn't they ?
We've actually gone from encouraging goals (what wins in football) by giving strikers the benefit of the doubt on offside, to discouraging them, but disallowing marginal ones, just to pander to a technology that isn't yet good enough, and we're now saying his (her) big toe was offside, to me its ridiculous that football seems to want to prevent the whole reason we play it, goals.