It's a real pleasure to see so many members willing to share their experiences and importantly remaining positive in such a thread. I have no idea what it's like to be a teenage girl but in terms of your relationship with your daughter I can appreciate how wretched this must make you feel.
You seem pretty grounded and no doubt aware psychological support is available and beneficial. Respectfully, there's likely to be parent-child issues and this is obviously the time to work on those points yourself and with other close family members. I hazard to say we all have issues of one sort or another with each other.
However, there are also likely to be many issues of her own which you perhaps can help her with as a friend, rather than as a parent (although in your eyes you're always both!). It's hard as a teenager to know the difference and it's your job to support that distinction. In my opinion

All the best.