' Don't think about one thing too much until it makes you stress. Moreover,the problem is not about you. '
I had been in your shoes, where our responsibility as a friend tested. We afraid that they will think we are so busybody about her, we afraid that they will not listen to our advice, and the most awful thing is our friendship will end for only that reason. (Sorry for not specifying the reason)
Let me give you some advice. Try to talk slowly with your friend. Give your best advice that might not hurt her. The best way is by changing her believe on that particular thing. If after that, your friend is still doing the same thing, means your advice does not affect her a bit, just let it be. You've done your responsibility. It's all up to your friend.
Never expect much. You're not the one who will change your friend's attitude or behaviour. It's their choice. We, as a friend, as a good friend, must pray for their changes for a better one.
I, me, myself is still in learning process. I admit that there are so many things that I must learn and explore. Please and please guide me.
Regards,
E.