I’m not sure what the use of changing that first part would be. Now, that second bit there is how I originally had it in my novelization. But then I watched the director’s commentary on the film, which surprisingly changed my mind. Having them be reverse images of each other (daughter of Vader, son of the Emperor) makes their dyad more interesting. Using the term “clone” would break that parallel. But I suppose it might be worth it to explain a bit of her father’s backstory.
The other thing we have to keep in mind is that her father looks nothing like Palpatine in the flashbacks. And we definitely don’t want him to say “a not-so-similar-looking clone of the Emperor”. Or drop the word “standcast” with absolutely no explanation what the hell that is. Lol.
May I propose the word offspring? That is to say he could be interpreted as being the son but that particular word leaves enough ambiguity that it still applies to being his strandcast.