I'm not usually one for drugs, but the thing that helped me get out of extreme social anxiety (I had selective mutism into my 20s), was anti-anxiety meds (off-label Modafinil). I didn't take it for long, but being able to be in a social situation without that feeling of dread and anxiety was actually mind blowing.

It helped me recognize a state of mind where I didn't immediately go to massive anxiety. After that, with therapy and forcing myself to do more social interactions, I got into a much better place. I still have some anxiety, but it's largely manageable - and most people think I'm quite social now.

It's something you might want to consider talking to a doctor about. I don't think anyone should have to suffer from social anxiety if there is some option to help them get out of it.