Go for it! If you don't want to wait, go vegan now.
Sorry, your aunty is wrong - humans don't need to be carnivores. Healthy vegan food is the best thing you can give your body!
You will need to take a b12 supplement though - although you don't want to take supplements, it's really important that you do. Your body can't make its own - if you don't get enough, all sorts of nasty things can happen... you can lose concentration, memory, and it can affect your nervous system. Your body stores for a while, so you wont need one straight away, but you will need one if you're planning on making veganism a long term thing. You can get it in fortified soymilks and cereals, or take it in tablet form. It's produced in a lab, it's not from animal sources.
Other than b12, you can get everything you need from plant foods.
Another thing to watch out for is iron - there are 2 types - heme (from animal foods) and non-heme (from plant foods). Non-heme iron is harder for our bodies to absorb, so try and get lots of it and combine it with vitamin C to maximise absorption.
fitday.com is a good site if you want to check if you're getting your RDIs.