Stranger Things never does anything by accident, and there are some concrete hints that Vecna might have had a secret human host to do his bidding. Ms. Kelly could be feeding intel about her students to Vecna, who's only been targeting high schoolers with known traumas. She might be willingly sacrificing them, or far worse: she's an earth-side host for Vecna, just as Will Byers (Noah Schnapp) was a host for the Mind Flayer in season two.