Hello Plenny, I'm so sorry to hear about your friend. It is so painful to watch someone we care about be so self destructive. You can see how twisted her thinking is in that she told you she would kill herself on the night you threw her a birthday party--just because she would 'show you'.
It sounds as though you and her other friends have tried to help her in the past. Perhaps form the same group again and try again, but really--she isn't going to change until she is ready.
One thing I want to assure you of--you are not the bad guy. You are just someone who has healthy boundaries "sorry, I will not be spending time with you when you are drunk". This in no way, shape, or form makes you evil, heartless, or cruel. So please do not accept the guilt trip on which she is trying to send you.