You know what girlfriend and boyfriend is? It's two people with their own differences, own minds who accept each other not try and fking change each other. Now stop trying to change her and just focus on your own diet and all that. Or sooner than you think she'll leave you.
There's so much more mate about your girl than food.
Look at those qualities. You're missing out on so much more about her and focusing on one thing and though it is important to you, it's not for her. It's about finding more about her thinking, appreciating, and if you had two life times it won't be enough to know everything about her and same with her with you.
You're taking about animals being killed, birds, and yet you are paying taxes, which gets millions of people killed around the world. We all do but we don't do anything about it.
Life is telling you something, when there are different people of colurs, beliefs, opinions, and the four seasons are not the same. That you embrace all of her not just part of her, but all of her and let her know you love all of her and not make her stressed out.
She has dreams,. goals, passion, and a lot more. Look at these. Get to know your goal and not let this come between you both. Forced judicary does not change anyone. It only makes them rebel. Let her see your example, and you live by your example, change your life, be excited about it and not talk about it. Just do, look good, feel good, and just live by example.
It's funny how we will take so much crap from work, from what we don't like from jobs, business, life, from government but when it comes to relationship, we so uptight about it, we want to change the person.
If you wanted a girl who is pure vegan then you needed to be honest with your core values from day one and date a girl who is pure vegan. And if transition happened afterwards - you live by example and let your example speak for you and not make her feel bad about it.
I am arab, my girlfriends are christains. I hate alcohol but I don't say that to her. Her family and her eats bacon and I don't. She knows I don't agree on this belief but I take all of her and her family. We still eat together, laugh together, it's ok. We even joke about what we believe and one guy called me Terroist to push his luck but no matter how hard he tried, I just smiled, joked and bantered back.
That made her love for me stronger. Showing her I'm stronger than all that I don't like and anything her family and world says, and our differences.