OP's list
Breakfast - porridge/granola, greek yog, fruit/ eggs - 300-500cals
11am - scone/biscuits with coffee 300-500 cals (based on just 2 chocolate digestives and a latte being about 315 calories, a full on scone with cream and jam would be at least double, that's assuming just a normal coffee with ss milk too)
Lunch - veg/pulse soup. bread, cheese, salami (400-600 cals)
3pm - scone/biscuits tea 300-500 cals
Dinner - Spag bol/curry etc 800-1500 cals - again, depends if just a tomato based curry and a bit of rice, or a creamy one with bhajis, naan etc.
Sweet treat, coffee - 300-600 cals
Supper - toast (150-300 cals)
So for the absolute most conservative estimate we're talking at least 2550 calories a day, which is much more than the average woman needs.
If you eat double that (and possibly double the max 4500 calories) that's a ridiculous amount of food.
and regardless of how much you eat, it is not enough for anyone to be literally 'starving,' after a day or two.
In terms of etiquette, even if she felt helping herself to food after being specifically invited to do so was rude, how anyone can think doing so is more rude than going home and slagging their host off for starving them is mind boggling.