How does Esther learn to take control of her sexual identity?

I think that the issues surrounding Esther's sexual
identity revolve around other subterranean conditions that plague Esther.  Essentially,
Esther does what is expected out of her and is never questioning why she does what she
does.  She scores good marks, works as a prestigious intern, and fulfills all that is
required of her.  It is at this point where she begins to delve into a realm of
questioning of her identity and who she is.  From this point, it seems that everything
is fair game.  Like so much in this social setting, there is a belief that all profound
questions can contain easy answers.  These answers are reductive in nature.  For
example, Esther sees her choices as work to be "number one" or to marry and have kids. 
There is little complexity in these options, and this is what drives Esther to question
everything. Her sexuality is a part of this.  I think Esther examines the issue of
sexuality because everything else is being questioned in her life.  The message that
comes out of this questioning process is that individuals must understand their own
identity and who they are, of which sexuality is a part.  It would be another "easy"
answer if Esther were to quickly capitulate to the idea of being with another woman as
solving all of her questions.  She does not, as demonstrated in her rejecting Joan's
advances.  Sexuality is shown to be something that is a part of, but not something that
controls, an individual's identity.  The ending of the story is one where Esther has
understood more of who she is and what that entails.  In "being born twice—patched,
retreaded and approved for the road," Esther has gained a fuller grasp of her identity
and who she is, of which her sexuality is a part.