Thank you for your responses. I really appreciate you taking the time to reply.
Some anxiety is good, it means you care and it's important but the balance has tipped too far. Recently DD has a music exam. By her own efforts, she was extremely well prepared. Talking to her teacher and accompanist, she was going for top marks. However beforehand she was consumed with nerves which got the better of her in the exam and she made mistakes she's never made before. She was devastated afterwards. Straight afterwards we went out to lunch and shopping as a big distraction. Just downtime and fun. We talked about it being something to learn from, how we knew what she was capable of and was so proud of her effort and that even though beforehand she was so scared she did it anyway. When the results came in she crumbled all over again. She didn't get top marks but she still did very well. We acknowledged her frustration that she knows it wasn't her best but under pressure she still did fantastically well. We don't want to dismiss her feelings but we don't want them to be blown out of proportion. As parents, we don't get cross or angry about the DCs results or demand they meet a certain level. We see they are trying their best and putting the effort in.
She puts so much pressure on herself with her school work. She's very self motivated and has to work very hard to get her good results so she has a great work ethic. But the stress is too much. We are very careful not to add to it and for her to know she has our support.
Like a PP said, I think you need a good amount of downtime and doing things you enjoy to allow you to cope with stressful situations. Even trying to make that happen is stressful as she feels she should be 'preparing for an exam or doing homework'.
These are just a couple of basic examples. There are so many instances which worry and nerves are dominating her life. When she does well, it doesn't boost her confidence.
Sorry for the rambling post. I'm worried about my worried DD - but I try not to show it and make things worse!
I love her so much, she's amazing- I just wish she could see it for herself.