Let me answer this as i also dont like her
1 she is annoying ( darling , darling , darling , darling, darling, darling , darling , darling , darling darling )
2 she do not hesitate to kill her partners
She was always the only survivor when she ride the franxx
She also tried to kill hiros friend
( ok she might be a yandere , but that does not mean that you have to kill )
3 she took advantage of others ( hero to be
precisely)
Remember that she was searching for her childhood darling ? She was just taking advantage of hero to find her darling before she knew that it was hiro all along