Volkswagen Golf 2010: Piston crack

My daughter purchased a 2010 VW Golf 118TSI in mid-2015 with about 45,000km on it. It was a one owner and had been serviced by a VW dealer from new. First, the DSG clutch had to be replaced at about 48,000km, which was funded by VW, but now at 51,000km she has been told that piston 4 has cracked and the bill will be $6700 to rebuild the motor. The dealer has advised that VW will not provide any support for this repair, which seems to be contrary to the Australian statutory warranty laws. Are you able to provide any suggestions as to what action we can take to seek VW support on this issue?