In actuality, the OP is the religious one- who is adamant on believing meat is food- it is a kind of carnism he was raised and brought up in, and not realizing that he has been massively brainwashed into the religion of meat since birth: by the media, by marketing tactics, by the entertainment industry, by the animal agriculture industry, culturally. If you tell little children that meat are dead animals, they will not eat them. Instinctively, they understand that it is wrong. But most of us grew up without that choice. We weren't told what we were eating were dead animals, we were told it was food. Children will eat whatever their parents tell them. That's how we grew up. That's how our parents grew up.

It seems pretty clear that OP and the gf do not share the same morals and vision. It's analogous to someone who is supposedly a "perfect bf," but he goes around molesting children. It's not a "choice" it's a difference in morals.

The gf has a right to find someone who has similar morals. Similarly, I wouldn't consider racist, homophobes for a romantic relationship either, just as I wouldn't consider someone who doesn't see that "meat IS murder" because unquestionably, and objectively, semantically, and culturally, it is murder.

That's why they call it a SLAUGHTERHOUSE. What do you think happens there? Rainbows and warlocks magically turning cows, pigs and chickens into a pot pie?