Gina is Tony's younger or as Tony puts it, kid sister. He is very protective of her as seen when he beats a guy who is with her in the Babylon Club and when he kills Manny for being with his sister. Gina is one of the two family members Tony has in Miami, the other being his mother, who unlike Gina does not take kindly to Tony. One of the things Tony does for his sister when he rises to the top, is buying her a beauty salon. A little later in the movie, Tony gets a distressing call from his mother saying that Gina has run off. This of course make Tony go straight to his mother's house where she goes and tells him the address of where she followed them. Tony goes to this address, only to find out its Manny's home and Gina half naked upstairs. Tony, of course, lets his anger get to him and before Manny can talk, he kills him sending Tony off the edge. He gets his goons to take her with him to his mansion. Later on, Gina comes into Tony's office, and within seconds, starts shooting at him. They are both unaware of the hitman on Tony's office balcony who comes in shooting and kills Gina. Tony kills the assassin and comforts his already dead sister by saying he is sorry and that he loves her.
In Scarface: The World Is Yours, Gina can be seen at the start of the game she is in Tony's office on the floor dead also when the the B button, or circle buttion is pressed and Tony starts to talk to himself he will mention Gina saying he loves her and that she's his guardian angel. Also as an exotic, her ashes can be bought as a decor and put any where in Tony's mansion.