She is not a child. She is an adult. She has chosen her path in life. It doesn't matter how she got to be the way she is. She will continue to be the way she chooses to be. When you make your own decisions in life and choose wrong, it is nobody's fault but your own. Welcome to adulthood.

You and the missus need to get together and formulate a plan for defending yourself against her. She will very likely flush her life down the toilet. That's her choice. The only question is whether she will take you down with her.