As expected, he doesn't manage to explain himself at all, and his pretense of sympathy makes her skin crawl. "Oh do you," she says disdainfully, not making it a question because there's no way he could understand. Grimly, she adds, "I would have taken him with me to my universe." So no, she wasn't going to get accustomed to this place for Gabriel's sake, and humiliating is hardly the right word for his betrayal.

The TARDIS is natively completely unconcerned with what ifs, since all possible outcomes exist equally to her and once a decision is made against one course of action, it ceases to be part of reality. But in this case, she would have been the one to decide, and her actions would have introduced something destructive and unpredictable to her universe. Not on par with Zagreus' catastrophic potential, of course, but Gabriel would have murdered and disrupted the order of her universe according to his whims, and it would have been her fault. It's a horrifying thought.

Which is why she doesn't think it for long. This isn't about Gabriel, it's about getting back at Zagreus. "And why are you protesting this universe so vehemently?" she asks with renewed force. "It can hardly be more antithetical to you than mine, and you of all people had better get used to existing here, since you won't be leaving it with the rest of us."