Simbo - DS had a month like that before the exams started. Paralysed with fear, unable to even open a book, crying constantly etc. I was extremely worried about him and concerned that he would fall apart in the exams.
I think each child needs to work out for themselves what is the best exam technique for them. DS has discovered (rather late in the day) that he prefers talking subjects through with a friend, rather than reading on his own. At least he'll know for exams in the future! One of my friends with a DS with the same problem, reads the revision notes out loud to her DS with him lying in bed, when he is so overwhelmed that he cannot even bring himself to look at it.
I have been making sure my DS eats well and giving him a daily multivitamin with iron, as well as liberal doses of "Rescue Remedy" as required. I have been trying to coax him out of his room - not always successfully; and switching off the modem and taking away his mobile phone at night to maximise the chance of him sleeping.
As soon as the exams are over, I'm going to sit down with him and construct a list of learning points re exam technique and revision, so that hopefully he doesn't get himself into such a state in the future. I have also booked him in with some sessions with a counsellor so that he can thrash out these issues with someone objective.
Hope you can get through the next week with your DD. (It is only an extra week, isn't it?) The thing is she probably knows more than she realises. At this point I'd say a BBQ and a big bowl of ice-cream sounds like a really good plan.