Pinpointing OP's current level of performance would require specific ranks across her subjects. However, from the information provided, and given my familiarity with SMSHS's current HSC cohort, I can offer some insight.
OP's internal performance does not appear consistent with a 90+ ATAR. While there has been some gradual improvement, it is unlikely to have resulted in rank improvements significant enough that they would ensure sufficiently high Assessment Marks across her subjects. With that being said, I doubt that a 90+ ATAR is completely out of reach, although I will note that it will be a difficult challenge. Favourable performance in the HSC exams will allow OP to improve her overall performance across her subjects and increase her chances of achieving either a 90+ ATAR or an ATAR closer to 90. This will of course depend on the specific standard at which OP performs in her HSC exams, not to mention that marks considered favourable can differ across subjects. For example, considering OP's subject combination, mid-high band 5's in English Advanced and Modern History as well as band 6's in Mathematics Standard, Legal Studies and Biology would constitute favourable HSC exam performance. However, maximising her chances of achieving her ATAR goal would ideally entail aiming for band 6's across her subjects.
As I mentioned, this will be difficult, although there is plenty of time to study before HSC exams start, so it is worth trying. Additionally, one should keep in mind the possibility of having adjustment factors applied to their selection rank (depending on university and degree). In the event that OP fails to achieve a 90+ ATAR, she may still be able to have a 90+ selection rank.
I hope this helps!
