I'm so sorry. Did you apply for the extra time she is allowed, and would any other access arrangements help her? Is she having lessons? I'm in the south west and will help out if I possibly can.
I have a pupil with ASD who failed with 59 a few terms back. I was a bit shocked because I thought he would pass, but he has difficulty processing all aspects of a question at once. For example, he will begin writing out a given scale, before noticing that it's meant to be descending, in semibreves. We worked really hard on the bits he didn't do so well in, and he managed to pull it up to 76 the following term.
My colleague once entered someone who totally bombed on the day, scoring only 21%. She, too, passed on the second attempt.
O I have, and I remember another girl, who had been taught inadequately in the past, and failed twice. Her mum eventually sent her round to me, but only wanted to pay for 4 hours of tuition. I had my work cut out, as in my opinion, this young lady should have been working towards grade 3, not sitting grade 5 yet. But together, we managed to do just enough to get her over the pass mark.