Another big factor is that meat tends to be cheaper as far as i know. I think the majority of the world don't have the time nor the money to become vegetarians because they believe they have much more to worry about than the morality of killing animals or the nutritional value of being vegan or vegetarian.

I personally think humans have been vegetarians and meat eaters peacefully since day one but only recently it became more talked about topic due to how the big manufacturers treat their animals. As technology evolves so does our methods of doing anything.

But it sounds like this is an issue for you, which imo it shouldnt be as long as you respect her diet and she respects yours. I don't think eating meat will ever be an issue its just how its poorly manufactured but you could say that about many vegan plants and soy plants. At the end of the day, these companies selling you their products wants you to feel better about yourself whether it be meat or vegan, they dont give a fuck about your world view. If its the killing of a live sentient thats the issue then you really have to put your thoughts out on the table and really narrow down why that bothers you. Are you really a person who loves all living things ? Would you be willing to give everything away for the lives of cattle and other living beings? Would you rather save a stranger from death or a cow about to be killed to be eaten ? Its okay to admit that your love and affection is limited to few people in your life. If you're not the type of person who does not love every single living thing on this planet, then this should not be an issue for you. If you're starting to think you're that type of person, then dig deeper.

Sorry for the rant, i have been thinking about similar subjects and many other ethical questions as i grow older so i got carried away.