In many ways, Megaera was used to the shifts. The Underworld could shift, and while generally the layout of it's chambers could remain the same, where the chambers would be might be different. So finding that this place had a counter where previously it had not was not so much odd to Megaera. Nor was she really minding those mortals around her. After years and years of dealing with shades, all of them more or less blended together. She was here because of what they called pizza.
Like most of the Underworld, food was not as much a requirement, and she could survive on Ambrosia and Nectar if needed. But she'd found now she was here, this place Zagreus had near torn down walls to get to, she could at least try and understand why Zagreus was so fascinated with it all. Which included food. She'd run through the frozen yogurt (an acceptable thing to drag people to, because she quite enjoyed the the frozen aspect of it) and was now onto the other options. As she had the luxury of time, she was not rushing through them either.
So far this was acceptable, and she had already ordered some to bring with. Both Zagreus and Thanatos might enjoy this. So she had not noticed the mortal until he spoke to her. Her focus shifted to him at the question, and while many mortals blended she did try and keep up with theirs. She could still not recognize him however, save knowing he was plucked out from his own home, much like her. "It is going nowhere, considering I am sitting." Questions like that sometimes escaped her. "Unless this place decides to move, that is." It could happen. Even the chamber she shared with her sisters moved on occasion.