Yes, one or two other issues to consider…
As
Batterytraveller has said we have only the joint media statement to go on, plus the PM’s words at yesterday’s presser, and the National Plan. I used those 3 references for my commentary at post #10,703 above: happy to be corrected but there is really nothing else yet (and some of the media coverage isn't helping) so you have only indications in lieu of firm guidance on what is changing. Issues to ponder:
Citizenship: If your UK traveller has Australian citizenship or PR as well as British citizenship, fine. If not then the lifting of the inbound and outbound travel ban in Nov may not help her – the relaxing of restrictions applies only to Australians so foreign nationals will (by implication) still need to seek an ABF exemption to come here. And there is no explicit confirmation that arriving non-citizens, even if vaccinated, will benefit from home quarantine when it starts – though it would be a nonsense to discriminate.
Timetable: Until the international restrictions on arrivals are amended (‘in November’) current rules apply and all arrivals, irrespective of vaccination status, go into 14 days of hotel quarantine. In your scenario, choose the flight arrival date according to your best estimation of when Victoria will enter Phase C and introduce home quarantine: it can only be a guesstimate right now.
Vaccination: As a person vaccinated under the UK programme your traveller will have received a TGA-approved vaccine and should have no great difficulty in having this validated for Australian immigration purposes.
Home quarantine: As the Commonwealth has thrown this one to the States, until Victoria announces a model (even a trial) then you have only the PM’s announcement of 7 days being the expected model, plus the reasonable assumption it will need to be in premises where isolation is feasible. You can look at the SA & NSW trials but really anything else about how it will work is conjecture.