AITA for perhaps not following social etiquette with food?
My wife (37F) and I (41M) were recently invited to a gathering with people we do not know too well. This was for Mother's Day and it was where everyone brings a plate of their own.
When we got there it was clear that everyone else knew each other quite well. Anyway, my wife spoke to the other ladies there and I spoke to the men. It turned out that it was also the birthday of one of the men in attendance. A cake was brought out and everyone sang happy birthday and the cake was cut. By this point all the food was already laid out on the table and, once the cake was cut, people started serving.
My wife was indicating that it was time to leave and I agreed. However, our son (7M) was still playing with the kids there and didn't want to leave just yet. While waiting I reached out and got two spring rolls and ate them. My wife seemed agitated at the time but I didn't really understand why.
Later my wife spoke to the main organizer there about us leaving early and the main organizer told my wife to wait for a bit as they wanted to take a picture with all the mothers in attendance. Our son wanted a slice of cake, so my wife got him some. I got him some juice from the table when he asked for it.
Anyway, once the Mother's Day picture was done, we finally left. However, upon leaving my wife angrily told me I was being rude by eating at this party. She didn't seem to have an issue with anyone else, but she says we were outsiders there and we were unaware of the birthday party or some of the other things that were planned.
From my perspective I feel like this was a party and people had already started eating. I feel I didn't even eat a lot. Where I might be the asshole is if I was breaking some social convention as we didn't know anyone well and perhaps I should have read the situation better.
My wife has been making snide and sometimes nasty comments about this for a couple of days now. Apparently, I do this at other parties too, but she doesn't seem to give me any examples. I gave her one example where I might do this (breakfast table at church) but she says that one is somewhat acceptable. I haven't really responded to her much but this seems to be continuing and I'm at loss really. So AITA?
EDIT: Update posted in a comment.