This is excellent -- so well-characterized and vivid. I just can see the hotel, the bar, and of course, the cliff.
The pairing makes a lot of sense, and you do a wonderful job showing us the damage both girls have sustained. And yet, as they do for each other, you make them beautiful. I've never been happy with the way that canon is so dismissive of both Millicent and Marietta; their stories have always seemed to me so much more complex than canon shows. And now you've given them the nuance and possibility they've lacked.
I love the way you chart the development of their relationship though how they do and don't look at each other. Very IC for both of them, since in their pasts, being looked at has never been something that has turned out well for either of them. Great line: It's like they are always taking turns watching each other, Marietta thinks as she stirs her drink. One is looking, the other looks away. What would happen if they were to look at each other plainly, at the same time? It is an unsettling and intriguing thought.