Vegans should have no reason to defend themselves, it is meat-eaters that have reason: Thus they make up every excuse ever thought up as to why they must eat meat.
Try to see these moments as opportunities to educate other people on Veganism. Many people have misconceptions of what Vegans are, so try to educate them as best as you can. Make sure you do a lot of research so you can have answers, and if you dont have an answer be truthful and tell them you will find out that answer.
Be a happy Vegan and smile, talk with an upbeat tone, be polite even if they aren't. Though your presence as a Vegan alone may get some seeds to grow, educating people about this lifestyle and what it is all about may help people understand you, and maybe spme people will give Vegetarianism a try themselves one day because you planted that seed.
My entire family is full of meat-eaters, and I dont have many vegetarian friends, but I do have a 6-year old niece who is an aspiring Vegetarian, when she makes the change I'll be there for her for sure.
As for your Aunt, if the moment comes up: Tell her what these animals go through, or get the movie "Earthlings" with that movie she can see for herself what humans do to animals.
I understand what you go through. My father is Anti-Veg, and thinks we are all a bunch of brainwashed people. Though I have to laugh at that because really it is the dairy, egg, and meat industry that has brainwashed the world as we know it today.
I often had fights with my dad and it is very hurtful of what he says, but he knows I'm never going to turn back and this is who I am, so he has eased down a bit. Most of my other family members respect me for what I am though dont really understand it.
I have a great aunt or something in my family who claims to love animals, drinks organic milk, and says she is mostly vegetarian but eats meat in the company of friends and family it seems. Yet she wears a fur coat :/
Anyway, try to be a happy vegan, educate the people around you! We're here for you. <3
Also might I suggest this podcast? http://feeds.feedburner.com/VegetarianFoodForThought
The first eps are at the bottom of the list so it may be good to start from the bottom and choose episodes that apply to you. I've learned a lot from her and she is very inspiring!