It was completely understandable that Marguerite was having a difficult time with all of this. So Elphaba just remained silent, letting her process what she'd all ready been told in her own time. Really, Elphaba would have sat there with her all night if that's what it took. At least the city wasn't crawling with Autons or anything else trying to kill them all right now. It was quiet on the apocalypse-and-Seal-craziness side of things, and Elphaba really welcomed that. Not that she'd done much of anything while the Autons were wreaking havoc since Anakin had sealed both her and Elena inside their house to keep them from going outside and getting hurt. Elphaba hadn't exactly wanted to go outside during that. And then there was the whole thing with Moriarty that she sort of still hadn't dealt with.
The currently non-green-skinned witch was still feeling guilty over everything she'd been made to do for that man. Having to protect him and anyone else he wanted. She might have had powers that would've let her kill him instantly, but when he threatened Galinda? She couldn't stand up to him. She wasn't willing to gamble on the fact no one would hurt Galinda if she killed Moriarty herself. In her usual Elphaba state, she didn't directly deal with the after effects after telling people that she'd been the witch that had been protecting him. Maybe if she'd spoken up about it sooner...well, that was no matter now.
When Marguerite started asking questions, Elphaba focused back on her. The first question wasn't unexpected.
"It is very common. Not exactly something everyone is used to. But it's just something you grow accustomed to the longer you are here." Which sort of segwayed into the whole 'there's no way home' topic, but Elphaba would wait for Marguerite to bridge that topic.
"No, I'm not surprised. I'm not from this place either. I come from a very different land called Oz." She wasn't expecting Marguerite to know what Oz was, Elphaba was just being truthful. She had no reason to lie about where she was from, so she didn't. It would also perhaps eventually lead her to telling Marguerite that her skin was actually naturally green. Though she'd save that for when Marguerite was less in shock because the particular revelation could completely send her back into shock. Or to hate her or be afraid of her or something, and Elphaba didn't want to put the other woman into such a position.