So she's planning to potentially traumatize Rose for life to help her?
Hibai's job is to make Rose stop protecting Benika's father (one of their targets)
The way Babylon see it atm, Rose is only protecting dad because of her love for Benika.
So if their relation sours and they break up, Rose would no longer have a reason to protect him.
Since one of the condition for this is to also not turn Rose hostile against them, Hibai is trying to guide Benika into learning that Rose murder people for her job and think that Benika would break off their relation as a result.
Though she got a bit impatient with how hesitant Benika was and chose a bit more impactful method at the end there (to have Rose straight up come and show off her skill in a hostage rescue situation)
Hibai isn't helping Rose nor Benika, she's just doing her job.
p.s. I think Benika's hesitation is more that she herself is surprised at how 'ok' she is with the revelation, and not Hibai's thinking that Benika is still refusing to accept the truth.