There is actually: Just don't train Cecille lol, if you follow any other route she is going to be alive.
(Opinion/rant incoming)
Honestly, despite how sexy the scenes are, Cecille's route is definitely the worst for me (not worst on quality or story or anything like that, worst as in the one with the most chance of shit happening later on), I'd rather take Elena's route where Mars, Elena and Erin get absolutely fucked up in the head than giving power to the blonde bitch.
EDIT: After some shower thinking, my opinion changed a little. Elena's route is definitely more grim, I only just remembered that Cecille was kinda coercing Erin into attacking the village in Elena's route so yeah, Cecille's route is a little better, if only BECAUSE Cecille got fully subservient to Mars. That all said, my point still stands that Cecille is a bad BAD person (Lol, even the bad stuff that happened on Elena's route was her fault) and giving her more power is far from a good thing. Rant finished.