I agree. This story should be expanded. It feels like a beginning to a longer fic rather than a vignette. I think the vignette form works fine within canon, where the reader can fill in the missing details. But when you get into AU territory, I think a longer form works better.

She ends the story too abruptly. I'm sorry, but that's not an ending. Nothing is resolved. The monster isn't found. The meaning of Scully's dream isn't explored, even though there is a hint that Monica would like to hear it, Scully never gets a chance to explain it, and Scully wading into a swamp doesn't do it for me. There are some good metaphors floating about but they need the weight of a finished plot arc to make them fully resonant.

I love the potential of the fic: the interaction of the three women is fascinating. Who are Sam and Monica to one another? What is Sam to Scully? Clearly not just a partner. But it's all too vague and unresolved for my taste.