sorry, I find "i am ssoooo freacking out i cant remember how to do anything" very amusing which is then reinforced with "i cant remember any formulas", not the fact she is stressing out over the HSC which is perfectly normal.
Like I said before just focus on the questions which have had the most re-occurence in the past HSC exams if your at this stage and having alot of trouble, and to also try maximise your marks i.e. 12/12 for the first 3 or 4 questions. And then try pick up some marks after that to total your raw score to like 60% then it will be scaled and what not and it shouldn't be too bad. However there is no doubt that at this rate your maths mark isn't going to be too good, so try and get your other 8 units to score amazingly in the exam. Also a good technique is, during the 5 minutes reading time, look at the easy questions which you know how to do then start off with them, this then builds confidence along the way, and as the confidence builds, formulas and other stuff will just naturally come to you.
Thats all I can say, further more, I think the reason your not remembing any formulas or anything is because of the stress your under at the moment. Take some time off, like maybe have a whole day without study. Then get back into it after.