That's really kind of you. I'd never heard of the Digger - Pioneer Index. And I didn't have the first pre-marriage child Andrew. Thanks for that.
I have the marriage and death certificates for Anna/Maria from the BMD. The marriage certificate gives just 'Germany' as place of birth, the death certificate (with info given by her daughter Catherine) says 'Tyrol, Austria', a part of the world that passed in and out of Bavarian hands - so my guess is Bavaria, but sadly that's only a guess.
Since I first posted I have (hopefully!) identified her in a passenger list from Liverpool and (even more hopefully) on a steamship from Rotterdam to London. None gives place of origin and I'm running out of options.
Thanks again for your help.