Its really hard when your the one watching from the sidelines. Its even harder watching the one you love, make the biggest mistake of their lives. I do know though that in the end things do work out. You will be a stronger, better person one way or another.
Keep your chin up high, and remember this is not your wife. Keep a positive mind and always see the good in any situation. It may be harder said than done, but that was what helped me get through all the BS that my H throw at me (and he throw me lots). Sometimes a person does need to reach rock bottom before it gets better, and all you can do is pray for their safety. And sometimes thats the best thing to do for them and yourself. This is where the detaching comes into play. It allows you to watch without interfering.
Take this time to REALLY focus on you. Make this all about yourself and not her. I'm thinking about you.
I saved my marriage and so can you....Its all about positive thinking...
