chicken duh
the egg. dinosaurs layed eggs and came before chickens
to the thread title: she came first. if not, you didnt do a good job
neither it evolved from a Dinosaur to a Chicken, so the Dinosaur came first, in case you didnt know - Birds were originally Dinosaurs, so Dino's still live among us...as Birds
evolution started as a single cell organism so i would say the chicken is boss, egg is a way to reform.
I made the same argument last time on this topic. Many people argued with me because of the literal interpretation of the question.