Hi Zutsuri!
Online you can find a bitsy hack to add a choice directly in the dialog.
I’m a basic user of bitsy so, uslually I try to find solution with standards command. In that case I would use a sequence list for the dialog.
First time the dialog will say: “next time you’ll talk to me the game will end!” And in the second time you talk to it I made it happen.
Hope it’s helpful! :)