Tell you what, get the minimum hours for F/O (required by CX) then join as an S/O you and your girlfriend can check out HK and see what you think, if you're having a good time stick with it and use the S/O roster for you both to see asia using staff travel.
If HK isn't your cup of tea just yet, or the flying as S/O isn't, you can apply for PAX F/O AMS or FRT F/O EUR (Less $$$ on FRT !!!) as you have the hours for F/O already and you will have the "CX way" under your belt.
However, if you opt for the PAX F/O AMS you may have to go to the bottom of the senority list again, ie resign and rejoin (a paper work exercise) as I believe a current S/O with the hours for F/O is taking a Sydney base out of seniority so he's basically being rehired as a direct entry PAX F/O SYD.
Hope this helps.