My initial reaction is yes she is too young to potentially go to bed hungry, but then she is so clever and aware in so many other ways that I don't want this (which is hopefully just a phase) to become a big long term issue.
Dd2 has always been a really good eater (and still is with breakfast and lunch) but over the last couple of weeks she has started to refuse her tea and just asks for different fruit, biscuits, ice cream etc. She definitely does have a sweet tooth, but she has always eaten savoury meals well too.
With dd1, 4.7, we refuse pudding if she won't eat a meal we know she had always liked, but I can't remember when we started taking this line with her?
Is dd2 just too young to get it and for it to have the desired effect of making her realise we mean business!