Sci-fi short story, AI on ice planet asking to be shut down

This is either a short story, or a novel (but most likely a short story. I don’t remember it being long). It is about a girl (I think quite young: 10-30 yrs) living on an oceanic ice planet. On said planet there were some primitive human settlements (stone age – medieval tech level). There was a constantly ongoing famine problem – vegetation was scarce. It is notable, that the girl uses her small boat (kayak sized if I recall).

After some introduction, the girl meets a space ship traveler, who claims (I’m not sure if he tells this immediately) that he is an AI. He wants to be shut down, because after a long time (hundreds of years) the AI decided that it doesn’t want to continue living. Because of internal programming, they cannot shut themselves, and they have killed all the humans (only overlooked this planet). It is very clear, that the AI is practically begging to be shut down, as it simply cannot die. If it’s damaged or in a state of disrepair it is compelled to self-repair. Any suicidal movements are also blocked. It is implied that there are many more (AI’s) like this. It looks like a human. Dialogue of the AI with the girl resembled a talk with the devil – the AI was tempting the girl with all kind of stuff (I’m not 100% sure about this last sentence, but I recall there were some offers).

The girl refuses to shut it down, but later on, there are some gigantic oceanic plants sprouting all around (growing from the sea bed all the way up to the surface).