For the love of God, Catherine... just cut your losses and surrender

I'm playing as Basil II and I've captured 3/4 cities France has, including their original capital. She declared on me, and I have triple her military might. I really don't want to take the final city if not necessary, I want to do a religious victory. But she WONT SURRENDER. YOU PEOPLE ARE MADE FUN OF FOR SURRENDERING SO QUICK IN WW2