Are you quite sure the head said the form was for the appeal?
I only ask because there was a case in your LA last year where there seemed to be confusion between "review" and "appeal".
we waited....after 3 and half months we finally got a letter saying we had failed a Head Teacher's review. WHAT?
What Head Teacher's review???? We didn't even know there was going to be one. Not only that but they used our appeal bullet points, of extenuating circumstances and academic evidence and discussed it. They were bullet points - simply said things like, 'incidents occuring in both tests' How could they possibly decipher what this meant? No wonder we failed that, and how wrong to use our info without us being aware. Had we known we would have written our appeal out in full.
Then after waiting all that time for an appeal date they said...'do you want to appeal?'
If the form is for the appeal (or for both review and appeal), you will get to see a copy a week or two before the appeal hearing - the problem is, if you find it doesn't say as much as you hoped, this may not give you sufficient time to seek alternative evidence (an EP report, for example).
You could try asking the head for an advance copy - on the basis that you're going to see it anyway, and it would give you more time to prepare your case.
If you feel unable to approach the head at the moment, do you know (or can you find out from the LA) when the appeal is likely to be? If it's not until late June, for example, it might be easier to approach the head if you leave her in peace for a month or so ......