I think that depends on what was promised to her. Just a tin foil hat thought, but what if Bianca
was infected? I don't remember it saying that vampires are excluded from infection.. Not saying that it does and I missed it.. ...
I don't see that it matters to a Nemesis-agent what was promised to Bianca: she's too unreliable, not trustworthy. I suspect she was -- in part -- directed to engage Harry and neutralize him (turned, Ramp-addicted & enslaved, or dead) as part of a test, to see if she
did have the power & finesse to handle a powerful (if young) White Council wizard. Remember Ortega's role as an "observer" -- both to witness violations under the Accords, but also I suspect to study Bianca's suitability.
OTOH -- borrowing your tinfoil to don a hat of my own -- if Bianca was Nemfected, then she becomes "trustworthy" and could surely have been a trusted avenue to further Nemfection!
I don't see that we have any real "information" either confirming or denying that Ramps are/aren't subject to Nemfection, however (nor whether Bianca herself was/wasn't). One could read the text and find passages to ascribe such meanings to... but that opens the door to almost anything.
FWIW, I'll re-mention my own WAG -- every bit as tinfoiled as yours (if not moreso)! -- that the
Lords of Outer Night are somehow related to the beings at the
Outer Gates.