Rosie, you sound well-prepared. That all sounds great. Your DD is now a bit sick of practice, and picking up on your vibes. I think you need to take time out, relax, forget about it, what will be will be, everyone has off days/weeks.
Just say to her you're sure she'll do fine in the exam. After all, will doing any more preparation really make a difference? No, you said yourself, she knows it all now.
And if she fails (not that she will), it's not the end of the world. She'll still be bright, healthy etc, and after all many "failures" go on to have happy successful lives.
(Not that I'm not stressing etc etc myself over my own DS...
But it's easier to give advice than to take it.)
PS SVE I have fantasised about ripping the lid off DS as opposed to the DS, but have thus far managed to restrain myself