Gina is not Gina, she is really Adriana La Cerva (The Sopranos). after Silvio drove her to the woods, he fired a shot in the ground, but didn't want to kill her. So instead, they killed Joey Tribbiani's sister, Gina and Adriana took over her life. That explains why she looks different to what she looks like in Friends. She then moved to LA and convinced Joey to move as well so they could be closer to each other.