I'm from Syndey, now live in the UK. Don't intend to go back. Things people might not realise about life in Oz: I worked really long hours there and there is a real culture of presenteeism so I doubt they have caught on to working from home, flexible hours etc.
As some others have said, very blokey macho culture.
Books are really expensive as they tax non Australian authors heavily. Actually in Sydney everything is expensive! Nearly had a heart attack last time I went back and ate out! Unless your friend is really well off she's likely to be living an hour or more away from the beaches.
It can be too hot in summer but also rains more and gets colder in winter than people realise (plus there is no central heating - even in the current energy crisis my house is still warmer in winter!) Also highest rate of skin cancer is the British expat population - the sun is 100 times more lethal, you can get sunburnt walking to the bus in the morning.
Which reminds me - terrible public transport. Long live the tube!
People in Sydney can also be really cliquey and there is a good chance your friend will just hang out with other British people.
Also roasts - it's too hot to cook them half the time which I personally think is a travesty!
There are lots of lovely things too - I miss the harbour, the beaches, some aspects of the lifestyle for sure and of course I could write a long list of all the great things, but it's not paradise, it's just another place to live. So don't assume your friend is off to an easier, better life. Moving overseas is incredibly hard and the culture shock is there even where you speak the same language etc. Book yourself a nice roast lunch somewhere and forget all about it!