Zagreus doesn't really have a good answer for her. That pretty much is why he'd accepted her invitation, that and boredom. And no small amount of curiosity; Gabriel is a consummate liar, and possibly deranged. Who's to say what actually happened in their dealings and subsequent fallings out? Was she also so emotionally invested, or is she just worried about potential hostilities? She's already suggested the former, but confirmation is only a knife-twist away.

"Well, there are two sides to every story, and I thought the side that explains how you came to consort with a murderer must be particularly fascinating. Try to focus on the elements of regret and betrayal, those are my favourites."