In Shakespeare’s play The Merchant of Venice the father-daughter relationship between Shylock and Jessica is something that is never clearly expressed in the entire play. In fact, the conversation between Jessica and Shylock has been rather scanty. But Jessica’s speech before other characters like Launcelot sheds some more light on this.

As it comes to Shylock, he behaves very decently with his daughter. He is not seen to utter something hurtful to her. Even we see him rebuke Launcelot when he yells by her name. Shylock seems to be very proud of his Jewish ethnicity and religion, and proactive to protect everything he’s got including her daughter.

Again, Jessica seems to have respect and gratitude for her father. She speaks mildly with him. And when Launcelot was leaving his service, she expressed her concern for Shylock. But even then, she utters that the house has become a hell due to her father.

I am sorry thou wilt leave my father so.
Our house is hell,

Apparently surprising, Jessica is seen to be ashamed of being born to Shylock. She is feeling a kind of guilty for not being true to her father and her religion.

Alack, what heinous sin is it in me
To be ashamed to be my father’s child!

But immediately after this, she argues that she is okay with him on a person-to-person level, but on the ideological level, she wants to part from her father. She is more ashamed of her father’s ill-manners and stubbornness rather than he being a Jew. Interestingly, her father does not know all these and thinks her to be a very obedient daughter.

But though I am a daughter to his blood,
I am not to his manners.

So, what she does not like is Shylock’s rigid nature. She is desperate to break away from the restricted way of life that his father promotes as a hardcore Jew. Jessica wants to enjoy the freedom of Christian lifestyle. And that is why she decides to flee with her Christian lover, Lorenzo.

This may bring a sense of sympathy in the readers’ mind for Jessica to be born to such a father that she cannot lead a free life, cannot spend freely and even cannot peep through the window to see the ‘Christian fools’ dancing and singing.

But, we have got to sympathize with Shylock too. He has always protected his identity and his home and lived with his head held high even after receiving so much torture from the Christians. So, it’s difficult for him to bear with the shock seeing his daughter gone with a Christian whom he has hated all his life. Again, some readers feel that it is Shylock’s own fault of character that leads to Jessica’s elopement and he deserved that shock.

To your first question, I would say we are meant to sympathize with both Jessica and Shylock in their respective situations, as already explained. And, I would say ‘yes’ to your last question that Shakespeare has been ambivalent in portraying Jessica’s character with both good traits and the opposite.