i hear you stalingrad. do you have a school that she should definitely get into as long as no disasters? what's your state option like?
my strategy is confidence boosting "you're ready" "you can do this" "if it's the right school for you, you'll get in, and if it's not we don't want a place anyway and 7 years of stress when the work is too fast"
then post exam in the waiting period i'll be dropping in a bit about the numbers vs applicants. how a wait list place isn't a no, just a "we want you but we have to work out the numbers". how siblings, junior schools, sports/drama/music scholars etc get priority blah blah (even if not entirely true). just to prepare her a bit. how everyone ends up at a good school in the end. i've already been telling her about x,y and z in dd1's year and which schools they did / didn't get so that she isn't too devastated by any rejections and knows it is normal. I'll also be telling her all the pros of the state school she should be allocated to. I've always positioned taking these exams as just giving her more choices rather than being lumbered with whatever the council computer program allocates her.
GOOD LUCK TO YOU ALL !