I am in the same situation. I am in Australia on a Working Holiday Visa and my gf is on a student visa.
My job code is 261313. We have been living together for less than a year. My EOI is at 90 points for 189 visa, with 10 points for being single.
I am hoping to get an invite soon. We would like to marry after lodging the 189 visa so that we both get PR at the same time.
The partner visa sponsorship will take about 20 months and I do not want her to wait that long. Whereas if I add her as a dependent on 189, it will be cheaper and quicker.
I consulted a migration agent and she advised that marrying after lodging the 189 visa would be viewed as misrepresentation as I was single when I got the invite.
Can you please let us know what is the best option for us?