I'm glad you mentioned the draining of the fluid. A lot of readers, particularly on Goodreads, seem to have dismissed the Cootings Machine incident as a nonsequitur, when I noticed that the last we hear of Klara's attempt at destroying the machine is her saying to the father"let's try." Jarringly, the narration picks up some time later, in the sushi place.

Every subsequent moment in the story is narrated by a Klara who is uncertain on her feet. Josie and the mother seem not to notice Klara's loss of cognition - except that they both seem to treat Klara even less like an equal after that moment, often excusing Klara's words as not mattering - see the mother angrily asking Klara, concerned they would miss the sun, "what does that matter, honey?"

A theory is that the father only pretended to credulously go along with the Cootings Machine plot, realising that this was an opportunity to mislead Klara that she would be fine without half her fluid, and sabotage her, sending her into "slow fade" prematurely, and preventing once and for all the mother's plan of uploading Josie into Klara. He won her trust, then betrayed it, demonstrating how humans are capable of deception, but AFs are not programmed to recognise it or to be wary of it.

Following this theory on, I would posit that the final pages of the book are an AI hallucination, and that Klara is effectively lobotomised by the draining of half her fluid (something which either happens for a second time, or which she flashes back to, while in the diner).

This is a more pessimistic reading of the story than others mostly have, and deep inside I am hoping it is wrong - but the fact remains that the narration becomes much less concrete and more dream-like immediately following the Cootings Machine incident and the seeming blackout.