If your peer was unable to continue her HSC exam due to illness, whether her Examination Mark will be used as part of the moderation process depends on whether she ends up submitting an illness/misadventure application and if so, whether it is upheld. NESA excludes, from the moderation process, students with an upheld illness/misadventure application and an Examination Mark lower than expected given their performance in the school assessment. Even if she does not submit an illness/misadventure application, her Examination Mark can still be excluded from the moderation process if it is much lower than expected given her internal performance, which will likely be the case if she did not finish her HSC exam.
The answer to your other question also depends on whether she submits an illness/misadventure application (and her application is upheld). If upheld, her Examination Mark would be either made equal to her moderated Assessment Mark, or it would be her actual Examination Mark, whichever is higher. Given that she is ranked first, it is more likely that the former will apply (especially since she did not finish her HSC exam). In such a case, her overall HSC mark would essentially be made equal to the highest Examination Mark achieved in your cohort, and her chances of an overall HSC mark in the band 6 range would solely depend on that highest Examination Mark.