"My friend was preparing a meal for the first evening when she announced she only ate fish now, no puddings and no chocolate."
For the life of me, I cannot understand why people with such specific dietary needs don't tell their host in advance of their visit.
A similar thing happened to me. My late OH had invited his brother, wife and 2 children, to spend Christmas with us. I was just bringing the Christmas food to the table from the kitchen when my BIL announced that his wife was now a vegetarian... we had been sitting and chatting for hours prior to this with me running in and out of the kitchen preparing the food... 
I did, as it so happened, have a couple of vegetarian ready-meals in the fridge because I also occasionally eat such dishes. However, I was hot, tired and had had enough, so I politely told her she'd have to make do with the vegetables and roast potatoes (of which there were plenty).
I'm just so puzzled why people think it's acceptable to give you such information quite literally at the last minute.