Which noun is the antecedent of the pronoun “she”? keiko is raising tulips because she enjoys flowers.

Keiko is the noun that is the antecedent of the pronoun "she" in the sentence. The antecedent comes before the pronoun, and in this case lets the reader know who "she" refers to.

In other words, you can change the pronoun "she" for Keiko and the sentence would have exactly the same meaning.

judy jones is an attractive woman who receives attention from many men throughout the story.   despite her beautiful appearance, she is superficial and callous.   she is an aggressive woman who goes after any man she desires but she is not happy.   she is fickle and is never satisfied.   her beauty is only skin deep.   dexter breaks down because he knows his dreams are unattainable.   he believes that wealth and physical beauty are what will make him happy.   he soon realizes that she has lost her attractive looks.   it is not all what he had planned.