Is it normal i just can't get along with my fiance's sister/i hate her?

So a lot of people tend to say, "When you marry your partner, their family becomes yours so you have to learn to love them too."

Sorry but that's BS. I never hate many people but this girl, this girl takes the cake! She is very self-centered and we have opposing morals on nearly everything.

Last year on thanksgiving, because she's a vegan, while we're all finding our places to sit down to eat the feast/the traditional turkey (that I made), she has the audacity to say, "you know I just have to tell you something before we sit down. i think it's really disrespectful that you cooked a turkey with me here because you know i'm a vegan and I am fully against eating meat."

I didn't know what to say so I just said "I'm aware of you being a vegan and if it bothers you, you are welcome to sit at the other table where the food is. I can clear a spot"

Then she just shook her head and said something like, "I can't believe you'd suggest that. How about next year we do some vegan thanksgiving dishes only. Like vegan sausage stuffing instead of sausage stuffing and a vegan chicken dish instead of turkey. I could give you recipes"

I nearly wanted to tell her to get out of my house after that. No one else heard her because she and I weren't near the others at the time.

She has also done this when she visits over my fiance and my house and she'll only want to go to vegan restaurants. I went to one only but I hated it because the food was bland as hell but I was nice about it, never even talked bad about it. Then the last time she's here I suggested we find a place with more options instead of strictly vegan and she was complaining the entire time she was there at the restaurant eating her salad saying she can't be expected to eat salad when she is tired of salad...

Like what do I do with this chick?? I just don't know. I can't even invite her to our barbeques as she refuses to come because she says they are "disgusting murderous celebrations of death" that's her phrase, not mine!

Normal or not? Are families like this ever able to function? She is always trying to convert me too and I refuse. I'm in school studying to be a dietitian and I know how bad it is to be Vegan but I NEVER mention that to her. I just say no, sorry but she'll get incredibly pushy!