lisalisa- missed most of this, and don't really have experience of normal toddler tantrums so no advice there as such. But food issues oh yes we do them. DS1 ate everything at 12 months, but 15 months he was only eating bread (literally). We took him off gluten and he has slowly expanded his deit. he will now eat gluten free bread, raisins, apricots, prunes, apples, chips (new addition) egg bread (new addition), chocolate, philadephia sometimes, honey, jam,yoghurts, buckwheat pancakes, soya milk and crisps. He used to eat satsumas but stopped after throwing up with a tummy bug after eating them one night and ditto smoothies with lots of fruit in them.
Anyway despite this incredibly limited diet he thrives! We give him supplements obviously (!!). We have recently seen a dietician, and she said although his diet is limited its fairly healthy- just a little low in protein (althugh egg bread has been added since then). So basically just saying don't stress. I used to get really wound up about his diet, but he won't eat anymore - and I find that he will add new foods such as eggbread every year or so! We hide stuff in his food. So i always make his bread with linseed and hempseeds added, and his buckwheat pancakes have grated cheeses in them.
If I was you I would offer her one meal- if she eats it fine - if not no wories. I tend to give ds1 a lunch I now he'll eat and then about every other day I dish up a "proper" tea- which is usually ignored. If he really hasn't eaten anything for tea then after his bath I give him a supper of toast and an apple -otherwise he wakes hungry at night. They don't need much to survive on. Honeestly the dietician was remarkably unconcerned about ds1's diet. She just suggested a few other ways of hiding various nutrients in the food, but otherwise said it was fine. Good luck!