She has all the faculties of a woman/female...it is unfortunate that her body rejects androgen that is needed for her to reproduce.

Why would you say she's of the 3rd sex?

Is it because your sister has an extra Y chromosome in her DNA?

She has a hormonal disorder but that doesn't mean she's a MAN.

You should RE-READ WIKIPEDIA or research more...because it is obvious that it is you have a problem with it and calling her a third sex.