How is Portia is a good role model for teenage girls?

Portia is a good role model for adolescent girls because she values her deceased father's wishes while also being independent and ingenious in her thinking, in a way that protects herself and others, as well.
After the death of her father, the man's will contained stipulations that Portia must marry according to her father's design in which the suitors would choose among lead, silver, and gold caskets, one of which holds her picture. The father hopes that this lottery will eliminate those suitors who are merely seeking her wealth. But, although she obeys the stipulations of her father's will, Portia is displeased with every one of her suitors. Fortunately for her, none of the suitors choose the correct casket, and they are all dismissed. Later on, Portia talks with her lady in waiting, Nerissa, and they both agree that a young man named Bassanio is handsome. Smitten by Bassanio, Portia pleas for him to stay for a while before he chooses from the caskets, because if he picks the wrong one, the penalty is dismissal. Bassanio, however, is too eager to marry Portia since he is attracted to her, but also because she also is rich and can pay off his debt to Antonio. So, he wants to choose the casket right away. Bound to obey her father's will and not divulge which one is the correct one, Portia cleverly has a musical piece played during Bassanio deliberation that may help him select the casket with her portrait.
After Bassanio selects the leaden casket with Portia's likeness in it, he is permitted to marry her. When the news of Antonio's losses comes in, Portia unselfishly sends Bassanio to help his friend Antonio. Bassanio offers Shylock six thousand ducats to release Antonio from the bargain, but Shylock refuses. Portia then goes to Venice dressed as a man and poses as a learned young lawyer named Balthasar to judge in place of Bellario, a learned doctor of law. While she works under pretense, Portia/Balthasar is, nevertheless, successful in preventing Shylock from getting his forty pounds of flesh, because she is clever in her judgement. She judges that Shylock can extract his flesh from Antonio; however, as Shylock is about to cut into Antonio, Portia/Balthasar interjects that Shylock must not let Antonio bleed, because the bond stipulates only a pound of flesh can be taken, not any blood. After Shylock relinquishes his knife, she tells Shylock to beg the court for mercy.
In addition to her clever use of disguise for herself and Nerissa, the women, still in disguise, get their husbands to give them their rings as payment for the successful services at court. When the men return home, they are accused of giving away their rings to other women, even though they promised to never remove them. But, before the matter becomes too grave, Portia and Nerissa reveal that they were the man of law and his clerk. Of course, Portia is to be admired for now having assured that Bassanio and Gratiano will be more careful about breaking promises.