It's quite interesting; anecdotally the most common partner for a Jew to have in an interfaith relationship is a Catholic. I don't think anyone has established, through any type of academic study, why this is. However, people have offered different theories.
Now, when we take a look at Vanessa and Nathan specifically, we find an interesting relationship that each of them has with their respective faiths. Here is how Nathan, for instance speaks of his Jewish educational experience, "Going to Sunday school and Hebrew school was not my choice... Had I been given the choice, I probably would have skipped out on both... My Bar Mitzvah... was a pain in the butt... Learning to read Hebrew without vowels was akin to pulling teeth." However, Nathan admits, "I am glad I was forced to go. It was helpful in my spiritual growth."
Now, Vanessa is not as colorful as Nathan. (Shocker!) However, she does not exactly go with the flow either. Though much of her education was in Catholic schools, she states, "My personal spiritual beliefs are always evolving... At this point in my life, I am much more comfortable having a personal relationship with God, rather than relying on a particular religion to tell me what it is I should believe and how I should believe it... I witness God’s presence in the world every moment."
So, it is not surprising that when you talk to this Jewish boy and this Catholic girl about what aspects of their respective faiths they most treasure, you get similar answers. What they most treasure are the interpersonal values their faiths teach. What they most treasure is how their faiths inspire them to conduct themselves in the world as good, honest, ethical people. What they most treasure about their faiths is how they emphasize not right beliefs, but right living.
This is where modern liberal Judaism and post Vatican II Catholicism find so much common ground. Don't worry so much about dotting the "i"s and crossing the "t"s of dogma. Don't fret over the fact that someone somewhere does not share your specific articles of faith. Do worry that there is injustice in the world. Do fret over the fact that many people everywhere are genuinely suffering.
It is this approach, right living as paramount, and making this world a better place as a priority, that perhaps brings so many Catholics and Jews together. It definitely brings Vanessa and Nathan together. In that, it makes them a fine example for their peers to follow.