Extension of Spouse Visa

Hi There,

I am Australian and my wife is British and has a 5 year Austrailian Spouse visa which was issued in 2013. I received a job offer here in the UK in 2013 so I moved to the UK and we've been living here together for the past 5 years. We have traveled back to Australia frequently during this period, and we have a 2-year-old son who is dual citizen (Aus/British).

Can my wife extend her spouse visa when it expires in August, or does she have to re-apply and go through the whole application process again?

Thanks.