It could be the usual 'fussy' stage of a toddler or it could be more.
As we've found out with DS, now 6yrs.
We think he has Selective Eating Disorder and have found www.fussyeaters.com to be a fab source of info and support.
It is not a website simply about fussy eaters but about specific food disorders.
We are now waiting to get DS referred to the hospital once we've moved counties in a few weeks.
It's been a constant battle with 'well-meaning' school/grandparents/my friends etc who all say 'don't worry, it's just a phase' but we now know it's more than that.
For DS, it started slowly after weaning and gradually got worse and worse until now, he will only eat a very narrow range of foods:
Plain pasta with butter on - no cheese, no sauce
Chocolate spread sandwiches
Milk /hot chocolate
Cereal - porridge/coco pops
Apple and cucumber (peeled)
Carrots - sometimes
sweetcorn - sometimes by the spoonful and others, never.
Lasagen - only from Tesco and ready made
Plain white fish.
Grated cheese
That's about it.
And that list isn't a regular list - he'll often go for a few days on just a few mouthfuls and won't eat anything that is touching something else or that someone else has prepared.
If you think your dd is like this, then it could be the start of Selective Eating Disorder or similar but the main thing not to do is force her to eat anything and you must tell your DH the same.
If you force her to eat "just a bit more/ just a few more mouthfuls", then she'll get more and more upset and you'll be pedalling backwards (this is whether or not she is simply fussy and 'trying you' or whether is's something like SED.
Simply, say "dd, have you had enough breakfast/lunch/tea?" etc, and let her then get down from the table.