The image I have in mind is that she's literally sucking blood from the wrist 🩸 While the blood bag idea gets thrown around, that shit has anticoagulants in it. 🤨 That's gotta affect the taste. That's why the Scarlets like it raw... Actually, what if vampire saliva itself is anticoagulant?

They can extract organic and tasty blood, and keep actually keep them too. Gotta label whose bags belong to who though. Would be quite disgusting to slurp blood mixed with your sister's saliva.