I've run into this from time to time. I don't tend to order dessert, especially if someone else is paying, unless the whole table decides to get it. But a couple times, I had a "friend" try to shame me into not getting something.
One time stands out in my mind. I was in my early twenties, and was meeting a co-worker whom I was friendly with so that we could hang out and get some shopping done. I'm kind of heavy, and she was...I would say 'average', but everyone seems to have a different definition of that. There was (and still is, come to think of it) a DQ/Orange Julius at the mall, and since I had skipped lunch I was dying for a smoothie. I suggested that we get something from there, and she seemed surprised. I was even willing to treat her, but I never got that far.
She said, "I don't really want to. I'm trying to fit into the next size down, and I've been doing pretty good."
I understood, but replied, "Okay, well, I won't be long. Where do you want to meet?" The day had gone pretty much like that; if one of us was going into a store the other wasn't interested in, we would split up and name the next store where we would meet.
She sort of scoffed, and said, "I just said
I didn't want to go there."
Now I was a little surprised, and said, "I know. You don't have to. But I missed lunch, and I'm getting something to eat."
"Yeah, but something from there? Do you know how many calories are in that?! I
don't need it, and, uh... *looks pointedly at me* you kinda don't either."
I got my smoothie without answering her, and she sniped at me all the way to our cars because I was "rude" enough to have it in front of her when she was 'trying to be good'. Just passing by places like that strike me as being a temptation, and I wasn't actually drinking it until we left. She was just mad that I had
it. I was "unavailable" for mall trips after that, and she trashed me up and down for being "unsupportive". Trying to tell me what I can and can't eat, and insulting my weight to shame me into obedience? That never works.