I can't really hate Haru because people who are in love are like that. They tend to become selfish. She noticed Tougo's feelings towards Natsumi and can't help but be jealous. Even though Natsumi selflessly devoted herself to Haru, it resulted to Haru being envious of Natsumi. Even when dying, Haru still chose to love Tougo and left Natsumi heartbroken. Unbelievable, right? But it shows just how much Haru loved Tougo more than her sister.
Where's the smexy stuff?! (╯°Д °)╯╧╧