Given that your teacher
(1) is female
(2) has said that she has many points against merit pay
There is a high probability that she is in fact against the idea of performance pay. There is also a high probability that she is a Labor voter. There is also a reasonable probability that she is a member of the AEU, a teachers union, which staunchly opposes performance pay, though the AEU have come up with their own "merit pay" proposal.
Assuming that your teacher is marking you, and that she has a negative predisposition to the idea of merit pay, the research on persuasion shows that she would mark you harder and be more critical of your work than if you argued a case that she agreed with. Yes, that is biased marking, and yes that is probably unfair. But most teachers do it subconsciously and don't notice it.
So it depends how much you want to risk. If you are in year 12 it's probably not worth the trouble.
If your primary objective is to get the highest marks possible with the minimum amount of input, then get to know her, talk to her a bit more, and find out what issues she is passionate about, find out her political positions, etc. Then argue a case that she would agree with. She won't notice it, but she would probably be much more lenient in marking you.