Abigail is the only character who displays genuine love, loyalty, and selflessness in the play. Above all, she remains unmotivated by money and appears to have some kind of moral code (although she is willing to dissemble if it will serve her father's ends). Abigail's dedication to Barabas is proved by her vow to remain loyal to him, following her conversion to Christianity.
However, we should be wary of regarding her conversion as a moral climax within the play. Marlowe uses Abigail's conversion to make a heavily ironic point about the corruption of the Catholic clergy—why would anyone seek to join a religion with such flawed affiliates as Bernardine and Jacomo? It even remains doubtful whether Abigail is a true religious convert at all, for she seems to appropriate Christian prejudice rather than Christian virtues. Her comment, "there is no love on earth, / Pity in Jews, nor piety in Turks," suggests that for all her moral worth, Barabas's daughter is as bigoted as the other Maltese. As James R. Siemon notes, Abigail undergoes a final "anagnoresis" or recognition of her own predicament that is a feature of tragic drama. She states "experience, purchased with grief, / Has made me see the difference of things." The "difference" that she refers to is a religious or racial difference. Thus, Marlowe suggests that Abigail converts to Christianity in a bid to reject her heritage, rather than through true religious belief.
However, Abigail is in many ways a romantic heroine whose relative goodness contrasts with the depravity of those around her—Jew and Christian alike. As with his other characters, Marlowe obscures Abigail's morals and motivations in order to complicate our responses to this character.