I was your dd in the same situation and age but I did move back after 3.5 years. Telling my parents I was going was hard. Is her dh from the UK?
We mostly had expat friends and found after a few years it was tedious/unsettling trying to find new ones when people moved back home and the Aussies mostly had their established friends already so were harder to get close to.
Also even very established families in Aus and NZ who had some UK roots seemed to spend a few years here and a few years there as jobs and family situations arose.
We moved back to the UK after thinking whether we wanted DC while we were still away from our families and decided we didn't.
To be more immediately helpful, the 12 HR time difference was actually more helpful than when I have worked with a 5 HR time difference away as there were more times when both sides are awake and not working. WhatsApp video calling is so easy and straightforward now and helps you both feel more together.
Make contact regularly and make some light touch, eg sending silly photos rather than every call needing to be a "proper catch up". Then it feels more natural and not a chore.
Plan a visit for their summer if you can. At least the sun will chase away winter blues.
It is hard to be so far away from your family though so I do understand you will be upset