A vegan? It might work.
This vegan? Well… She doesn’t seem to accept you if she even jokingly says you should go vegan. half-jokingly, ouch, it easily becomes a big problem later.
If the other person is you? Well, if you really have doubts and not just ask us because it’s an interesting question, you probably don’t love her so much (yet?) that it would have a big chance to survive all the differences. But maybe your relationship gets stronger later. And you don’t even eat animal products in front of her! If you are serious about this relationship and it works out, that will happen all the time, why not to start now? Maybe it will show you if she can accept that even short term. Because with time, big differences tend to cause bigger and bigger problems between people. Sometimes it gets better but often worse.
Many vegans accept their family eats meat, many even cook it! (I never went that far when I was a simple vegetarian but I didn’t have to and I had no problem with others eating meat, at least from good sources.)
Others are quite annoying even for a meal per year let alone living together long-term.
You should know what she is like. Try to eat your normal food in front of her, it’s a good test. If you want smaller steps, eat vegetarian but not plant-based food.
Ethic and others… I think we should have similar opinions to some extent. But… My own ethical and other reasons didn’t really changed. I was a vegetarian for long, I never ate much meat until recently and I do carnivore now. There is no problem at all. I am very choosy where my food comes from. I have some flexibility because I choose the less bad from two. If I had a choice, eating “tortured meat” or a HCLF plant food, I would choose my own well-being, I am this selfish. It wouldn’t be nice but I can’t suffer in a carb-poisoned state, starving even when I overeat, it’s horrible. If it was just 2 weeks, I might just fast but not for much longer…
I got carried away, sorry. Main thing I understand it’s not that simple for everyone. And it’s not just a noble decision, some getting used to and then everyone would feel great. Many vegans seem to think so. But it’s wrong. If someone loves us, they don’t want me SUFFER. And I don’t exaggerate and many of the folks here know that. I am even healthy enough, I handle plants moderately well, I can do vegetarian keto or low-carb if I must for a while, no big problems (I even can handle some plant-based LCHF days) - but it’s still way better without plants, at least most of the time. I need very low-carb, it seems. Many people need the same and the consequences for them are often way more severe if they overdo carbs.
If someone doesn’t understand it, I have a big problem with them.
Me and my SO eat very, very differently, now it’s stronger than ever when he often eats his plant-based carby food (temporal thing! I am the cook and I will figure out what to do as I always did, now it’s enough to handle my own drastic change) and I drink my coffee but will eat my carnivore dinner later. But it’s fine and dandy as we have no ethical differences, the practical ones isn’t too bad, we are both health-conscious and we don’t force dietary changes on the other (not like it’s usually possible between adults) because we think the other eats as healthy as they comfortably can.
If our thinking about things (nutrition, ethics, what is healthy for whom, respect for the other) would be vastly different, it would be a nightmare. Our own diet is our own business to some extent. Some common ground in the two diets helps a lot, though. Many people would find a big hole inside if they couldn’t eat the same food with their family. I love that too and usually do my best to prepare the same dish for both of us, no matter my actual diet but it’s really not the important thing. I am there at lunch, why does it matter if I eat something else or if I just drink water? We are together then. But we are different people and our (ideal) diet often reflects that.