My MIL is looking to come visit a Christmas 2015. She last visited in October 2014. It used to be the case you had to wait two years between tourist visas. I've had a good search on the immigration website but can find anything. Does anyone here know?
Am assuming your mum is a UK passport holder and had an electronic tourist visa - if so then you don't need to wait 2 years between visas. I have been to Australia 5 times in the last 6 years - just applied each time for a new visa.
Electronic Travel Authority visa (subclass 601) This visa is for people travelling to Australia: As a tourist For business visitor activities In most cases, this visa allows you to visit Australia on multiple occasions within 12 months from the date of the grant of the visa or the life of the visa holder’s passport (whichever is shorter) for three months at a time.