Check out the influence guide stickied above.
You have to beat her in three separate sparring-in-your-undies sessions in the cargo hold, then get her to open up about her mother. This option happens after you talk to Kreia about it after the second or third sparring session. Be nice. She likes light side talks. It's not really that much of a romance IIRC, and don't let your influence with Visas get too high in the process. She'll get snippy and won't talk to you if you do. Women...
Be considerate to others or I will bite your torso and give you a disease!