@SlimLizzy - When you decide what you're going to eat; what are your deciding factors? Do you do a calorie count up beforehand, or is that count on a retrospective basis? Have you had another HbA1c test since you were diagnosed, to understand the impacts of your dietary trimming?
Secondly, even at 12-1600 calories a day, that doesn't "feel" to me like very much.
You are I are of vaguely similar volumes. I am 1.60cm, weighing in at c48-49kg. I eat LC, but not necessarily that LC. I don't count my carbs or calories regularly, but on the few times I have counted calories, I eat 2000-2500 in order to maintain my weight. Maybe you just need to eat a bit more of everything.
I don't have ABS, but if I overdo the fats, I end up with steatorrhea, which isn't pleasant. If I'm finding my weight slipping, I have to up my fats, but slowly.
Have you had a decent broad spectrum of blood tests, to test your vitamin levels and for any malabsorption issues?