It's definitely the lack of butter that's the biggest issue for her (closely followed by whatever she gets instead of the chocolate dessert). I guess it's understandable, and easier for the crew, but doesn't stop the margarine being any less disappointing!
I often ask the crew if they can find me a spare butter. If they can't, don't forget that there's olive oil available - which is probably slightly better for us than the butter anyway!
I've always had my dessert (or/and cheese) from the main menu in CW, I'm fairly sure it's not special catered. So she has just as much chance of getting chocolate dessert as the next person... ^