Concerns

How do I, as the mother of a grown woman, express the deep concern I have about her life and the way she is leading it?  Kristin seems so lost...not just in her relationship with another woman but in her regular bouts of excessive drinking.  And the worst is that she puts her children's life in peril each and every time she puts them in the car when she has had more then one drink.  Does she realize what her life would be like if her actions hurt or killed any one of them?  What she thinks is loss now would be infinitesimal by comparison.  She is 40 years old...how do I chastise her and what can I do about it?