You have described my 2 nearly 3 DD to a tee. She was a briliant eater but know she is just terrible. I'm lucky if she will have one or two bites of dinner. We used to battle her every night trying to get her to eat but it would just end up with everyone stressed and then someone gave me the best piece of advice - "It is up to us as parents to provide our children with nutrious meals but we can't make them eat it". Apparantely I survived on fish fingers and pineapple for years.
It is so frustrating but we are just serving her dinner, making her stay at the table while we eat dinner (if she doesn't want to eat that's fine but she has to stay at the table becasue sometimes she will nibble at it while sitting there) and if she eats her dinner she gets dessert.
With the chocolate she only gets chocolate in the morning and she can have an easter egg (yes they have already started arriving, ggrr!!) as her dessert for her reward for eating dinner.
One tip I have found that helps get DD to eat using her incredible amount of independence. Each morning I will put what I want her to be able to eat during the day, yoghurt,fruit, fruit bar, crackers and cheese on the bottom shelf of the fridge that she can reach as it seems that if she gets it herself she will eat it over me getting it for her.
Best of luck. Our picky eaters are enough to drive us crazy.