My friend has always been very into healthy eating - absolutely nothing wrong with that in the slightest, and good for her.
We went out on a day trip together and when it came to lunch, she said "I really need to eat some vegetables" and it ended up being my choice (between 2 places) of where to eat (there was 4 of us) and I chose a pizza place. She left the crust and said afterwards - all that grease will keep us warm now.
I also dared to buy a bottle of coke on the way home whilst she bought some fruit. She asked what I bought and said I told her and she just laughed.
Now I eat healthily 90% of the time but on rare days I generally don't give a shit and will enjoy pizza without getting upset about it. Life is too short to worry or deny myself certain food all the time.
I don't mind if she wants to be healthy 99% of the time but I don't want to be judged for what I decide to eat.