@Akera93 she didn't reincarnate as another person in this life, her identity is the same as the previous life for this one. In short, she just went back in time.
and I know it's weird that they call each other sister/brother... it's a language thing, there's no direct translation in English and so the nearest translation would be brother/sister 😅 basically it's how they call an older/younger relative/friend/(it can even be used to pertain to anyone)
also yeah the art is not as consistent 😂