Before, during, or after he defeated her in their first battle. It was very vague, but we know that Cilan did something very bad.
Nah. She survived so that says something...or he found out you can't write Death Notes on a notepad
Dento: DIE DIE DIE!!!!!
Corn: *sigh* He's at it again >.>
Pod: u_u Should we tell him that's just an average notepad?
Corn: ...No...remember last time?
Pod: ^_^ You're right! It'd take all the fun away!
On their second meeting, his salad monkey violated her flower deer in a very off-limits area. I don't think there could be a clearer metaphor. :P
he used two klinks, and made the pair go squishy-squash on her using gear grind, xplaining her hair...
He tried to cook her.
Killed her by writing "Cabernet" in the Deathnote, which he STOLE FROM L!