[That's actually a really peculiar response to Szayel. Is she just saying that to gloss over the subject, or...]

Are you familiar with Shinigami, then? [Pretend I didn't mess up my ordering and Szayel was clear on who is what.] But...yes, that certainly sounds about right for him.

[It's weird to have his history with Renji brought to light, but it's not like there's much sense in being concerned about it now.]

Oh, it was not something so petty as a blood feud. Though the Shinigami did invade our territory, so naturally we fought back. Renji had the pleasure of finding himself in my personal halls.