I haven't read the whole thread so I hope it's OK to 'pop' in. Dd aged 13 self harmed earlier this year. Nothing too serious thankfully and I don't think it's still going on. Although I freak inside everytime I see a cut on her she can't account for or the scissors are moved without explanation.
I went straight to the GP who referred us to CAMHS. We're waiting for the results of an ASD assessment. I have mixed feelings about that as she ticks some, but not all the boxes. CAMHS were very keen to have her tested and it does seem like it's the go-to diagnosis for anxiety, particularly in girls.
DD's anxiety is not too bad as she can attend school. She has a small group of friends who she sees out of school once a week. But other than that she doesn't really socialise which worries me. She always loved drama but now refuses to go. We removed all social media which she has now replaced with Minecraft for hours at a time. Or hours alone in her room. 
I miss her.
I find it hard to deal with and wonder if she's been pushed down the diagnosis route for something that's 'just' teen angst.
I took her to an event the other day where we were talking to lots of adults who vaguely knew DD, and to be honest her behaviour was very odd and I felt quite embarrassed by it. I know that's awful to admit and I would only do so here.
She refused to make eye contact and mumbled replies. I explained to a few people that she has social anxiety once she was out of earshot as I was aware of all the quizicall looks. There were a load of kids from her primary school there all hanging out together and she just refused to engage with them. I'll admit I felt a mixture of sadness to see all but her there, and frustration as she hung around me like a shadow but was behaving so oddly. She said she didn't want to go home though.
She's always had social issues. The lack of eye contact and discomfort with talking to people is new. But she's always had issues with making friends, to the point that she had none in her last year of school. She does seem to expect people to come to her though. One girl who had known her for her whole life came over and said hello at the event we were at, and DD wouldn't engage with her at all. I tried to get her to see this sort of behaviour is hardly going to encourage someone! The whole thing is so frustrating.