He doesn't hate her, he's much fonder of her than he is of any of his family other than his mother.
But the thing about Reiju is she's still a reminder of his dreadful childhood. Where she was a coward for the most part and, although not contributing to the bullying physically, went along with it for fear of being picked on as well. That's out her own mouth. And then as an adult, despite not being an emotionless brute like her brothers, still continued to go along with her families deranged outlook on life.
There's really not all that much to like about Reiju. Her love for Sanji is about the only redeeming part of her character. She actually knows what Germa was doing was wrong and went along with it for years.