Hi Anonymous Anna,
Often legislations will dictate that members of certain occupation must be qualified and registered in order to practice. This often involves proving that they have the necessary skills as well as the necessary legal safeguards such as the relevant insurances. It does not appear there is any such law applying to dietitians or nutritionists.
The Nutrition Australia website states that:
http://www.nutritionaustralia.org/national/resource/nutritionist-or-dietitian
"In Australia, professional nutritional practice is not regulated by the government, and there is no legal protection over the terms ‘Nutritionist’ and ‘Dietitian’ – anyone can call themselves a Nutritionist or Dietitian, no matter their level of training."
Assuming this is the case, I would therefore recommend that you simply get a good disclaimer that acknowledges that you are a student and do not yet hold qualifications and that you have no professional liability insurance (it would be ideal to have insurance, but I imagine since you are not charging much for consultations its likely out of the question). You can buy a basic health disclaimer at this website
http://www.lawanswers.com.au/legal-documents/online-business-website-legal-package-for-australia.7/- they can also be customised to accommodate your specific circumstances. Maybe start with that.