Greg Cox wrote:
The movie is ambiguous. When I chronicled Marla's death in my novel To Reign in Hell, I put it about four years after the destruction of the planet's ecosystem.
This was done entirely for dramatic purposes. Marla's death was a big deal; I didn't want to throw it away in the first few chapters of the book. Plus, if Marla was going to be the great love of Khan's life, whose death caused him to be consumed by vengeance, I wanted to spend a good chunk of the book on their romance, which needed time to grow and deepen . . . .
So, yeah, in my version, Marla survived on the planet for at least four years before her fatal encounter with that Ceti eel.
Not sure how they handled it in the comic-book version . . . . .
In the comic book, a faction that was against Khan finds a Ceti eel, puts one in a sack, then kidnaps Marla and puts the sack over her head, thus killing her eventually (this happens after the explosion of Ceti Alpha VI.) Khan kills the person responsible while Ceti Alpha V goes to hell from all of the accumulated asteroid strikes resulting from the explosion of Ceti Alpha VI
(not 'the shock shifting the orbit' as was said in the movie, and the reason why the person responsible acted against Khan-he believe that Khan wasn't acting responsibly as leader, and so used the Ceti eel to get Marla to kill Khan.)