My dad has been dating Cass for two years now and they moved in together in January of this year. Dad has me (17m) and my mom died 8 years ago. Cass has a 12 year old son and a 6 year old daughter with different dads and neither have a relationship with their dad anymore so we all live together all the time.
Cass and her kids have dietary issues with dairy and most meats. They can be around people who eat food with them but they don't eat any dairy or meat and they substitute a lot and cross contamination is a big deal. Cass has found it hard to eat out with the dairy issue and she found a place that is totally dairy free so now her and her kids have a twice weekly thing of going there. Once just for them and the second time anyone can join. Since Cass and has moved in with dad she has invited me to join them every Friday at this place and I have said no every time. I don't enjoy the substitutes I have tried since they move in and I cook for myself or dad cooks for the two of us since he doesn't always want the dairy substitutes either. He does it to support Cass and her kids and not because he likes it. I just skip meals with that and take care of myself.
For the last couple of weeks Cass has been complaining that I make no effort to join their weekly dinner out where anyone can join. She said we're all supposed to be acting like a family but I won't even figure out a dish I like in their safe place and eat with them. She has asked why I don't want to make the effort and her and my dad have argued about it twice already. I told her honestly that I don't like the substitutes for dairy and there's nothing that genuinely has none of them.
For context this has some kind of dairy substitute in basically everything and they have no regular dairy or the option to leave it out. It's not very fancy and the menu is pretty small too. The one thing I know it has that's dairy free is the salad which isn't a full salad it's lettuce and kale (I think?) but lettuce and one other green, so yeah it's not where I could get fries or something and just eat those.
Cass thinks it's unkind for me to not give this a try for them. I don't think it needs to be a priority. AITAH?