I know there have been a lot of posts on Dutch Nationality and after going through all (or all that I could find) there doesn't seem to be one for our exact circumstance.
This question relates to my partner who was born in July 1993 so we realise that if she is in fact eligible we don't have much time to actually get through this process, as she turns 28 in July.
My partner's mother was born in the Netherlands in 1958 and met her Australian father while he was travelling through Europe. They were married in the Netherlands in 1985 after which she he moved with him to Australia.
Her mother did not acquire Australian Citizenship until 2006 so when my parter was born in 1993 I assume her mother was still technically a Dutch Citizen (unless she lost it due to the amount of time living away?). My partner was not a part of her mother's Australian Citzenship process.
After going through all of the official sites it reads to me that because she was born to a Dutch mother (assuming she was still Dutch at the time) she was technically a Dutch citizen at birth and because she was born in Australia and therefore born into her Australian Nationality she did not lose that Dutch Nationality.
The one thing throwing me off is that when we go through the checklist for applying for Nationality or a Passport it asks for "Proof that your parent or parents had Dutch Nationality until you turned 18" (we don't have this as her mother obtained her Australian Citizenship, therefore renouncing her Dutch one, when my partner was 13).
Given that the official sources seem to say my partner shouldn't have lost hers when her mother did (as it specifically says "a minor is exempt if the minor is born and lives in the country of which he receives the nationality [Australia in this case]. This does not apply when the minor has made a declaration of renunciation of the Dutch nationality."), I feel as though maybe I am missing a point somewhere.