She will probably have to have a provisional licence but there is no time limit, she can take her tests as soon as she has them as long as she is 17.
If she gets a full Australian licence she can exchange it.
However the P plate rules vary between states so it might be more complicated. As I understand it some states you have to take a test to get P plates and others you don't.
If she has taken a test she may be able to transfer her licence for a full UK one - we don't have graduated tests for cars, you pass both tests and you can drive any car, no different speed restrictions or alcohol restrictions apart from the legal ones.
So she may get a full UK licence but have to wait until she is 17 to actually drive.
Alternatively check which licences she can transfer her Australian one for and see if there is one that can be transferred to the UK.
Eg a Malaysian friend could only drive for a year on his Malaysian licence, but he could swap it for a Hong Kong (I htink, it might be Singapore) licence, once he had his Hong Kong licence he could transfer that for a full UK licence.