Psychomum5 I had panic attacks really badly when I was 18. I was a wreck for months and gradually recovered over the next few years. I haven't had them since. I also had the chest pains, they're not at all serious physically, they just happen becasue of the hyperventilation, but I used to think I was about to drop dead and it just made it even scarier. My diet was good, my weight was normal. It was entirely psychological in my case, although there were some big physical effects aside from the immediate, including a huge ridge across each of my fingernails.
I was also very busy with lots of things outside school (in my case sports and work)before it happened; although they were there as a good escape and a release and they did help, just doing too much and wearing myself out might have helped tip me over from thinking I was quite happy and getting on with life into having constant panic attacks - but I suspect it would have come to a head sooner had I not been so busy with these things.
I think that the doctor may be trying to say this to your DD, but it may well make her think that there is something pysically wrong with her. I don't think stopping altogether is a good idea if she doesn't want to - it's quite important that normality continues as much as possible.
At the time this happened to me I couldn't have told anyone what the problem was as I didn't have enough of a sense of perspective on my life. There certainly didn't seem to be anyting 'wrong' that might have caused this, to most people.
I wasn't coping too well with too much academic pressure (internal and external) and very inadequate teachers. I'd also had some signs of being very stressed during my GCSEs before ad I'm still very nervous about exams, so I'm prone to stress in this area. My parents had a bad relationship and had actually decided to split up but had decided to try to hide it and pretend everything was OK so it gave me the best chance of doing well with my A levels, but the constant tension at home was palpable and it seemed very unreal that nobody was acknowledging it. I'd previously tried to talk to adults about how awful my home life was and then just feel like I must be such a bad person for saying such horrible things about my parents who were, and still are, both decent people. To cap it all couple of my school friends were being sexually abused and the fall-out from them trying to cope had left my previously great social life shattered.
It all seemed normal to me at the time (apart from the social situation) as I was too young to have any sense of perspective - I couldn't understand what was wrong until years later.
I agree that CBT is a good idea. I only found out about it much later, but I can see how it can help with this. Some reassurance about the mechanics of panic attacks would have been so helpful in the early days. If someone had just sat me down and told me about why I was dizzy and suffering from chest pains and shooting pains down my arms insetad of just telling me to breathe into a paper bag it would have been so helpful. Counselling at least, and asap.
I don't know if any of this would apply to your DD, but for me it was the combination of school + home + social life going wrong at once rather than one defined cause.
I don't know that there's a right answer about the SATs - saying that she doesn't have to do them might be like telling her she can't do them and only make future exams tougher. Saying that she's got to do them might be like telling her that how well she does academically is more important than her wellbeing and mental health. She needs to take responsiblity for being brave and doing it even if it's scary and she really needs something put in place to make it as achieveable as possible (separate room? it would depend on what would make her feel better able to cope).
For me, becomeing very needy and dependent made my parents co-operate so the panic attacks kind of served a purpose as well, as I realised a few years later. I sometimes wonder if I would have got involved in drugs or done something different if there hadn't been this 'benefit' from the panic attacks. Actually, the fact that they did look after me was probably a positive in the situation.
I hope your DD starts to feel better soon.