With predicted Level 5s and a "1" recommendation, I think you should give it a go. (Edited because I misread your post - I had the recommendations the wrong way round!)
because the average CAT tests were less that 121 she has only got a 3 ( Recomended with reservations ) although she has a 1 for attitude.
I think the "3" recommendation is highly dubious.
Heads are specifically warned not to base their recommendations on CATs (or other test scores), because they are not directly comparable. You can read the advice for yourself in the Head's manual - the first download on this page. The information about recommendations is on pp. 17 - 21:
I think that you can make that point politely at the hearing: "The Head based her recommendation on previous CATs results for VR, but we have been led to believe that the official advice is not to do that? ... (Wait for Chairman to agree) ..." It is likely to make the panel look more closely at the overall accuracy of the Head's recommendations.
You will receive a copy of the recommendations sheet with your appeal confirmation letter, so if you would like to post back then, we can advise you on how accurate the Head really was.