Quite a lot of this seems odd to me. I teach 2 subjects, one of which is 60% NEA, the other 100%. For both, we have to give the students the raw marks in advance of submission dates to the exam board, so that the student has the time to appeal the process before final marks are entered online. Note that I used the term "raw marks" because that's what they are. For the 100% NEA, I can show them the grade boundaries from prior years but always say that they can and do move, so don't count on anything. Moderation by the exam board can also change the marks, so this is only the start of the process.
I book an appointment with the exams officer where we sit together and she enters the raw marks onto the exam board's secure portal. Once she hits "enter", a sample is generated. The number in the sample depends on the size of the group: for cohorts of 10 or fewer, all NEA work is submitted, then between 11-20, it's something like 11 - sorry I can't remember the exact numbers. However, this always includes the highest and lowest marks. For the 100% NEA one, we have 4 assessors so enter their initials onto the portal so that the sample includes roughly equal numbers from each of us. I did this in the first week of May and have not heard anything since, which I'm taking to be a good sign because if I had screwed up, the board would want to see further work.
In the case of the OP's DD, whilst I can accept that mistakes happen and specifications change, the subject teacher and exams officer should have been aware of this. In my subjects I am a member of specific groups on Facebook for teachers of each specification and level, so as soon as something like set works in Music changes, this is plastered all over, discussed ad nauseam and posted in large letters all over the exam board's website.
My advice to the OP is to ask the school calmly if the wrong advice was given, what processes will be put in place to ensure this never happens again? Has the teacher received training on the current specification, or on the previous one? Does the teacher have external support if they are the only teacher of the subject? In Music, although there are 2 of us teaching it, we also know lots of colleagues in local schools teaching the same spec, so we can and do help one another out with moderating or checking process if necessary. Again, the Facebook groups are brilliant for advice and support. Finally, your DD should never have been given any grades, only marks. It would be worth following this up with the member of SLT responsible for exams as the correct process appears not to have been followed.