Title: Sea Change
Author: Kimberly Unger
Publication: Galaxy's Edge
Publication Date: September 2015
We see this story from Maryanne's viewpoint, and there's room for a couple of different ideas about who/what Maryanne is before she's spilled enough detail that we get the right idea. I don't think this is an accident, by any means.
The world is probably not Earth, but it is habitable, and humans are living more or less successfully on it. Unfortunately, they do not have all the infrastructure they expected to have; a major control and support facility on the moon (one of the moons?) has been destroyed. Maryanne and her cohort are supposed to defend the land against invaders from the sea, but she's doing that on her own now.
Jim Henley's review:
Another fine short story (~6.8K words), from the viewpoint of “Maryanne”, a bio-cyberdog caught between her programming and her attachment to a refugee family on a post-apocalyptic colony world. Unger gets the weltanschauung of Maryanne exactly right, and gives you the worldbuilding you need to appreciate the story without cheating the diegesis.