User blog comment:B214/Volume 22 spoilers/@comment-90.202.240.151-20161002221704/@comment-90.202.240.151-20161002222640

actually if she was an antagonist it wouldnt be for revenge but to take control of the underworld by manipulating issei to make her get into the government. It would make sense with Ajuka being the only potential threat to her she can take control. Lilith has had plenty of time to powerup posibly past sirzechs level of power.