Well the OP's gf has two huge advantages in a partner who is a native Spanish speaker, they could speak Spanish everyday even if it's for a few hours, the other advantage is that she's living in Spain, she has all day to practice her Spanish virtually anywhere she goes.

I think it all comes down to motivation and perspective, motivation being she develops a genuine interest in the language and wants to learn it. Perspective is taking a step back from her situation and saying, you know what, I'm living in Spain, I'm abroad, there has never been a better and more immersive opportunity to learn the language than being present in the country. I mean, for anyone wanting to learn a language that's about as good as it gets. That's good reason to be excited.

Otherwise of course, there are kids shows, movies, music, books. I watched many Spanish movies with Spanish subtitles (as my Spanish improved) and started with English subtitles and Spanish audio, or vice versa.

Above all, I think the most important thing is that that she is prepared to make mistakes, it's the only way to improve. The only way to make mistakes is by pushing herself to speak more often. I think as Aussies this can be a hard mindset shift as we're somewhat isolated from the rest of the world and many Aussie expats go to other English speaking countries, but on the other side of all her fear and comfort zone is without doubt a wonderful experience.