User blog comment:B214/Volume 22 spoilers/@comment-82.48.158.172-20161109231053/@comment-10330822-20161112235709

Except Rias has just traded half her peerage that she spent so much time training to Issei. How is that any different. If Bennia develops feelings for Issei and she wants to go, it is literally no different than say Rias trading Xenovia to Issei. Besides, I highly doubt Sona has put much training into Bennia as is, especially since she was her second choice.

Sona seems very focused on the happiness of her peerage, just like Rias, hence why she would never consider laying a hand on Saji because she knows girls in her peerage like him, in addition to her seeing him as a little brother. So, that only strengthens the possiblity Bennia might be traded to Issei, if she really wants to go.