It is to win her that Bassanio needs the money for which Antonio pledges a pound of flesh, and is Portia that controls the outcome of the play by preventing Antonio's death at the hands of Shylock.
Portia is not only wealthy and beautiful, she has a razor -sharp wit, which tells the audience at the very outset that she is not meant for a merely decorative role. Though Bassanio only as “In Belmont is a lady richly left,/And she is fair and, fairer than that word,/ Of wondrous virtues, (I,1) we see her ready wit and her scorn for lack of learning when she comments on her various suitors, Falconbridge for instance, remarking: “He is a proper mans picture, but alas, who can converse with a dumb-show?”.
This shows that not only is she herself intelligent, she is also looking for a savvy life partner, who could meaningfully engage her in proper conversation. Her sarcastic remarks about her suitors and others stem from her confidence in herself, she is secure in the knowledge of her own superiority. This confidence usually marks the hero of a story or play, and overtaking Bassanio and Antonio in shrewdness, wisdom, and initiative, Portia almost becomes the hero of the play.
Once she hears of Antonio's plight, she is brisk and matter-of-fact and knows exactly what is to be done, and in what order: “First go with me to church and call my wife, And then away to Venice to your friend; For never shall you lie by Portia's side With an unquiet soul. You shall have gold To pay the petty debt twenty times over”(III, 2). She is more like an action-hero in her manner than a delicately feminine heroine. She decides to go to Antonio's aid of her own volition, not only showing initiative, but also a large heart, another requirement for the character of a hero.