Bianchi

Bianchi is Gokudera's half-sister, as they share the same father. Bianchi, known as "Poison Scorpion Bianchi" or simply "Poison Scorpion" in the Mafia world, specializes in Poison Cooking, a technique that turns any food she makes into poison, regardless of whether or not it's intentional. Bianchi herself is immune to Poison Cooking and believes that she is quite an excellent cook. She is in love with Reborn, who was a former associate of hers, and wants to kill Tsunayoshi to free up Reborn's schedule; however, she refuses to kill him for the benefit of others. 

Bianchi is violent when it comes to her love interests, but is otherwise a kind person. She cares deeply for her half-brother Gokudera Hayato, always attempting to help him, and gets happy if he shows signs that he cares for her. As she gets to know Tsunayoshi, she begins to care more for the Vongola, as shown later. She is usually calm, in contrast to her brother. 

Reborn! Wiki.