Isabella is an actress that the Smiths hire to pose as Francine in order to go on a cruise in "Little Bonnie Ramirez".
When Francine complains that Roger's personas have lost their edge, he pulls one of a little girl out of retirement and frames Francine for kidnapping him. He sets out to impress her by defending her in court, as well as appearing as the victim, but things go badly and Francine is sentenced to four life sentences.
Meanwhile, the rest of the family was anticipating a cruise, but have a problem when they discover that the reservations were made in Francine's name and she needs to be present. Watching a television reenactment of the 'kidnapping', they decide to hire the actress, Isabella, to pose as Francine. On the cruise, she not only offers to help Steve learn to dance to impress a girl with dance moves that she learned in Johannesburg, but teaches Stan to stand up to the waiter that screwed up his drink order and rescues a drunken Hayley when she falls overboard.
As Roger shares his sad tale with Klaus, the family returns from the cruise where it turns out the girl that Steve was trying to impress was actually an adult stowaway thief. Isabella suggests that Roger will find happiness in being selfless. As they go to visit Francine in jail, Roger uses his speed to swap their clothes and positions so that Isabella is mistaken for Francine and returned to her cell while the rest of the family beats a hasty retreat. Hayley feels guilty about putting Isabella in such a position and how Francine should have gone on the cruise, until it's pointed out that without Isabella along, she would have drowned.
Isabella is voiced by Salli Saffioti.