We tend to make many mistakes throughout our life. We make wrong decisions, we trust wrong people and they might wreck our world. But that's life. As a friend, the best you can do is to support and be the backbone of your loved one. You give them advices and it is up to them either to listen or not. and when they need you the most, you never back off and say 'I told you so', because they are your friends. They are human being just like you. They also make a lot of mistakes.
A friend talked behind my back few years back. It is somehow humiliating me and giving a pretty bad impression to my other friends. I was heart broken and could not forgive myself for trusting such people though I never confronted her for the mistakes that she had done to me. The damage is done and there's nothing much to say after all.
Now, she did the same things that she talked behind my back before. The curse backfire some might say. I didnt utter a word about it, nobody knows other than me. I can choose to do the same thing that she did to me last time. but I choose not to.
"At some point, you have to make a decision. Boundaries don't keep other people out. They fence you in. Life is messy. That's how we're made. So, you can waste your lives drawing lines. Or you can live your life crossing them. But there are some lines... that are way too dangerous to cross."
Meredith Grey: Grey's Anatomy
Sometimes, some things are better left as it is. It just another lesson to learn; to her and to me. It just a part of life, to make mistakes and learn from it.