I think worrying about what others do or do not eat, and needing validation that slim women only stay slim by starving, is an unhealthy mindset honestly.
All women are different: our heights, our body frames, bust size, our metabolism, our past histories of illness or pregnancy, our gut biome, our unique emotional and psychological factors. The worst thing is to beat yourself up or look for excuses or reasons why your body doesn't look like another woman's body.
I will say that everything I've ever read or learned about weight and nutrition suggests that it's vastly harder to lose weight than to stay slim if you've always been slim. That's why something like 97% of all diets fail in the long run, and why the much vaunted "willpower" isn't a good tactic. The body holds on to fat, and once a fat cell has been created it can't be destroyed (only shrink) except via surgery or liposuction. So please don't compare yourself to women who might never have been larger.
I've been what most people would consider pretty thin my whole life (without consciously ever dieting or restricting calories), and IMO it's a combination of having a small skeletal frame, being flat-chested, never having been pregnant, metabolism, probably gut biome too, and then dietary factors. I don't have a massive sweet tooth or drink all that much, and eat mostly vegan, but do eat pasta, pizza, chips, potatoes, bread, etc. every day.
See I've always had this theory. I'm never really hungry and never really full. Most fat people I know are the same. Whilst the slim people I know get really hungry (hangry) and then get full and finish eating before their plate is empty.
I agree with this, or certainly it's true for me. I'm not sure if it's metabolism - maybe it's that thinner people are more in tune with their appetites/don't eat before they get hungry, and are also used to eating smaller amounts? I often find myself having to eat more frequent smaller meals, because I get stomach pains if I eat very much (volume-wise, not calorie-wise) in one go. I think your body just gets used to a certain amount.
On the other hand, there's a difference between being a foodie, and being emotionally dependent on food. I definitely consider myself a massive foodie in the sense that I love food and cooking and love discovering new foods and new restaurants. But I can also easily forget to eat if I'm working or focused on something. On the other hand I've gained a bit of weight during lockdown and am conscious that I've turned to food and junk since I can't do any of the things that normally bring me comfort and joy.
I'm not trying to give advice or anything because I'm not qualified, but some of the comments you've made - about feeling guilt and shame over food, but also feeling that you have no pleasure in life comparable to eating, and that you use food as a reward - well, it maybe suggests there's an 'emotional eating' aspect going on, and maybe a chat with a therapist might be useful? Rather than just dieting.
And please don't beat yourself up. It sounds like you have a really healthy diet which is the most important thing, and a size 12 is definitely slim. Unless your weight is causing health problems, it might be good to really address why you want to lose weight and what losing weight would mean to you.