There is a difference between n award and warning. You have to get 3 n warnings to get a n award (<50%, plagiarism, cheating, etc), and at that point you will be forced to repeat the course since it is considered a non-satisfactory result/non-completion. Or if you are doing 11-12 units, that course you will be forced to drop won't count. Principals have the last day on what you have to do, some are more lenient while others are rather strict, you might have to go to private consultations with head teachers/counsellor as to why you are not trying/lacking in performance.
What I do know is that University will not see n-warnings prior yr11/12. That is, any unsatisfactory result will not matter. Correct me if I'm wrong, but I'm pretty sure that is different for yr11/12. Universities will be able to see n-warnings however, most will not think much of it if your atar is high enough. That being said, an n-award will probably be pretty concerning for universities, and if you are applying to a highly-sought after course, it might have an impact. But again, if your atar is good enough, I don't think it should matter too much unless if the reasons you received n-warnings is through cheating/plagarism which does not seem to be the case here. To be sure though I would encourage your friend to consult a teacher, since they have much more understanding of his/her situation
N-warnings do not go away as you complete the coures, they are pernament, so out of 4 exams you cannot fail 3. Even if you get 100% in one, it is still not considered as satisfactory.