Kids go through various stages, and your daughter may be doing that (or
she may be discovering the power of making her own decicions <g>).
It's also true that some kids range from having no problems at all
eating anything all the way down to the other extreme of never wanting
to each anything that's touching anything else, or something similar...
some of those things I believe are genetic; but they may change to some
degree over time too.

Regardless, there are things you can do that should help, like some of
those already mentioned.
I would add to the bite-sized advice that kids will more enjoy any food
that's presented in a fun way, like a snack or dessert format, for
example (on skewers, cut into shapes, with a fun dip, layered like a
parfait, etc.... or anything on a pizza look-alike, or rolled up with
eyes and called a creature, etc., etc.); you should be able to find all
kinds of these things online, particularly in sites and groups that
deal with kids.

Another thing you can do if you're willing to take the time (and it
*will* take time) is to have her help fix the food, maybe even shopping
for it and being the one to pick out the perfect specimen.
Plan in advance how you can do this for a particular food, but most of
all let whatever you do be fun, don't get too goal-oriented, take your
time, and let her do as much as possible -- or the parts *she* wants to
do anyway.

At this age (and lasting prob. until they're 30 or so), one important
thing to remember in dealing with kids is to let them have that golden
thing called "Choice" in as many ways as possible.
This is not to say that they can choose to eat only ice cream and
cookies for every meal, but that they can choose whether to eat this
kind of sandwich or that kind of sandwich (from a list created by you).
It's really surprising how far this goes toward avoiding friction and
heels dug into the sand, since they can then actually *have* some
control over their lives; and if they get it in some ways, they'll be
much more willing not to need it over every thing.

Good luck!

Diane B.