From what I understood, the CP's death was inevitable. It was actually the stepping stone which made the FL to remember what happened in the original story and that allowed her to prevent her Mom/Sister's and the King's death. So no, the CP died not because she didn't do anything while knowing what'll happen, she was also unaware/doesn't remember the story at that time.
In the first place, she was never like the usual isekai protagonist who knows every bit of the story because what she had as a material previously was just a script. That's why only a major act in the original story made her remember the other things that will happen.
Composer/Producer guy was not bad, was not obsessive, and was aware about the status of their relationship. In other words, the perfect "fling".
Musician guy was also not bad, same as the composer dude minus the fact that he's kinda money hungry so that might progress to something bad like exploiting the uke or smt but whatever.
Apartment guy was already a red flag, obsessed and delulu.
And finally, Mister Attorney the final boss, how is the uke so unaware of the possible outcome when he was literally blackmailed by apartment guy? And now you're with a literal DISTRICT ATTORNEY for god's sake and you think everything will be fine???? UGHHHHHH
He's so smart and dumb at the same time, I'm stressed (╯°Д °)╯╧╧