I have a friend in the Phillipines who needs a new mobile for work. I have been told that if I buy a mobile for her in Australia it will not work in her home country. Is this correct?

As far as i know, it is correct. Each location and country has their own register system and codec and the device will not read foreign registers and transmitter signals and pulses.

Maybe some near locations would work out more familiar for instance U.S and Canada,  but since Phillipines and Australia has nothing in common i don't think it can happen easily.

However, there's an option which happens here in U.S you can bring a foreign registered mobile and give it to related people, they will update and create a register available inside the U.S soil. I am not sure about other places or the relation between locations. You can check this option between these two countries see if it can happen.