Hi, forums can be a bit daunting at first.
Re using a debit card in Australia, I have been to Australia 4 times and only on the first time did I take travellers cheques. Quite easy to change for cash using an Australian bank and taking passport along as identification.
The last three times I have taken some cash, just so I can get through the first few days and then have used a Hole in the wall.
As for communicating I used my mobile (vodafone) rarely but i believe that they have just abolished roaming charges so phoning from abroad should cost the same as a call made in the U.k ( you may need to check on this)
Hope the above is of some use
Hope your daughter has great time in Perth (Been there twice really laid back place)
RTW 2005