previous advice seems to be to not focus on the academic as she has already proven her academic ability by passing
Not sure where this comes from, or how authoritative it was.
The issue seems to me to be something of a grey area!
It makes perfect sense to argue "If you're qualified, you're qualified!"
However, if places are allocated according to score, it also seems to make good sense to try and argue (if appropriate) that your daughter was expected to score even more highly than she did. You would probably need a letter from the current headteacher confirming this, and any other supporting academic evidence.
Like Tracy I've no knowledge of the area in question - but presumably the headteacher does.
At an appeal you're entitled (with the possible exception of where a review has already taken place) to put forward any case you wish.
If in doubt, I would suggest putting forward academic arguments as well as reasons for this particular school. It's then up to the appeal panel to decide what to give weight to.