Why does Eduviges say "God willing"/"Dios mediante" when she talks about taking shortcuts to heaven?

On page 11 (English paperback)/page 10 (Spanish http://www.kkoworld.com/kitablar/xuan-rulfo-pedro-paramo-kko-esp.pdf), Eduviges tells Pedro that "The secret is to die, God willing, when you want to, and not when He proposes. Or else to force Him to take you before your time". "Todo consiste en morir, Dios mediante, cuando uno quiera y no cuando Él lo disponga. O, si tú quieres, forzarlo a disponer antes de tiempo."

Why does she say "God willing"/"Dios mediante" if she wants to go behind God's back?