Little Ururaka held out her arm, because she told Toga she could have her blood. Which was ultimately the only thing her parents had to do. That or let her continue to suck animal blood. Togas Backstory gets forgotten often, but she assumingly killed her first crush, the guy who looked like Deku, cause she could not keep it in anymore due to all the repression. In the flashbacks in season 5, we saw her drinking his blood while crying. However from the flashbacks we learned that, she fell in love with him in the first place because he was always bleeding due to him being heavily bullied, so NOW the question remains if she actually killed him or if she just stumbled upon him being extremely injured and just making the situation worse by sucking his blood. In the Manga, Toga actually tells Ururaka that she fell in love with bizzarro-Deku because he was always beaten up yet worked hard. They cut that part in the anime but left in Ururakas answer "i also think it's cool when someone works hard despite being beaten down", i guees due to time.