While it was possible that there had been movement while her eyes were shut, she didn't think it likely. Her instincts were honed enough that she was super sensitive to all of the noises in her general vicinity. Besides, Death Eaters weren't exactly known for being stealthy and quiet. Once upon a time they were forced to remain in the shadows sneaking around to fight their opponents. But as soon as the Dark Lord took control of the country, they no longer had to operate in the shadows. Their bravado and their assuredness that they would remain unchallenged meant that they lost a number of their skills in being subtle and quiet. She would've heard Death Eaters from a mile away.