Actually the conspiracy theories do include that she died, or that something went really wrong with the procedure and she is in a coma, or has not recovered, that there was domestic violence, that she has filed for divorce and removed herself, somewhere, that Prince William is the one who shot Thomas Kingston (although I am not sure how this would be related, and that the two brief sightings of Kate have been of her double. But it's not like there wasn't a conspiracy theory about a "double" in our government a few years back.
There is a theory that the obvious photoshop flaws are to distract from the fact that this is Kate's head superimposed (more expertly) on someone else's body.
Q