What are some of Tituba's character traits The Crucible?

Tituba appears mainly in Act 1 of the play and then briefly in Act 4.  When Tituba first enters, she demonstrates timidity and motherliness.  Whether her timidity is a natural or "nurtured" character trait is debatable because she is used to bearing the blame for much of what happens in the Parris household.  Miller, the playwright, notes in Act 1 before Tituba's first lines that she is

"very frightened because her slave sense has warned her that, as always, trouble in [the Parris] house eventually lands on her back."

Despite her obvious fear of Rev. Parris and other town leaders, Tituba does not let that fear interfere with her sense of motherhood which she demonstrates toward little Betty Parris.  As she enters the room where Betty lies in a coma-like state, Tituba is pained that she was kept for so long from her "beloved."  Unlike Betty's own father, Tituba does not think about how Betty's condition will "damage her reputation"; she is mainly worried about Betty's well-being.

Tituba is also a very spirited, entertaining character.  She must have been for Puritan girls to risk so much in order to listen to her tales from Barbados and beyond.  She is believable to the girls, perhaps in part because she is so different from the norm in the Puritan community.

When Tituba is whipped and threatened into confessing to witchcraft, she demonstrates the complete demoralization of a human.  She realizes that she has nothing left to save her.  One, whom she thought of as a family member--Abigail--has betrayed her, and there is literally no one left to defend her.  As a last resort she confesses and names names in order to protect her life.  At this point, she is certainly a desperate character, but like her timidity, this is a character trait that is literally beaten into her.

Finally, at the beginning of Act 4, Tituba shows a lack of sanity.  Perhaps her long stint in jail combined with her already superstitious nature caused her to lean toward insanity.  It would cause the same for most people.  Tituba's last words,

"Take me home, Devil! Take me home!"

illustrate that she is somewhat crazy or that she is so discouraged with what has occurred in the town that she believes it would be better to be with the devil than to be trapped in Salem.