I originally read this and felt that if the medication was working, and she really wants to go, the go for it. But I do think there is no hurry in getting experience traveling abroad. Shorter stints, in the summer for instance, can build a sense of familiarity. I think that during undergrad years, many kids with medical or psych. issues benefit from being close to home, even though I also believe it should be them, not parents, who choose that.
If your daughter really wants to go, make sure it isn’t a “geographic cure,” meaning that she has in her head that everything will improve with a move. She will bring whatever mood issues she has, with her.
If meds are working, that is a big argument for going.
Australia is pretty far away. If she is still used to a lot of family support, I would think about smaller steps or giving her more years to become more independent.
I would be wary of any chance of isolation. Otherwise, it’s kind of a 50/50 dilemma, so my sympathies!