They will deal with this matter in your absence and you will need to complete a document where you enter a plea of guilty and put to the court your mitigating circumstances (what they should consider in giving you a lighter sentence).
You should contact the course and advise them that she will not be available and will like to make a written plea of guilty directly to the Magistrate on the day.
They will be able to tell you what documents you need to complete and whether it is the practice to deal with people in their absence.
While you are speaking with them, I would suggest that you consider asking if they can bring the matter forward and you make your way to the court and appear before the magistrate.
In your absence you may be given the full disqualification period which means you will not be able to drive in Western Australia until the disqualification period expires. If you try and obtain a Western Australian licence during your disqualification period, if it is discovered it is the same as being caught driving whilst disqualified.
The court will deal with your matter in your absence but you should speak to them and confirm exactly what the requirements are.
Do you have the court details, if not, can you tell me the name of the court and I will provide them to you.