I have been trying to see if she can plead guilty now that the trial has commenced (because I thought she could).
As pleading guilty "should" reduce a sentence to some degree.
In NSW a person can .....
You can change your plea to guilty any time before or during the hearing, but if you are considering changing your plea, get legal advice as soon as possible. Legal Aid NSW
I think a person can in Victoria also, but this link is for the Magistrates Court, and I can't find a definitive answer for the Supreme Court of Victoria ....
If you plead not guilty and you change your mind, you can change your plea to guilty at any time. You should seek legal advice if you would like to change your plea. Magistrates Court of Victoria
(Though, obviously, a plea cannot be changed after a verdict. Every link I read said that.)
They do say that if you change your plea to guilty during a trial, you may have to pay the prosecutor's fees. Probably because you wasted the prosecutor's time. imo