Miss Winston was Derek Powers' secretary.
Miss Winston was an aide and a confidante of Powers; she was one of few people who was aware of his actual condition and helped him keeping up the charade. She also was involved in several of his crimes, including the attempted corporate sabotage of Foxteca via Inque, with her reporting on the failure of the more recent attempt. Powers sent her to pick up Paxton from Verdeza. After Paxton successfully exposed his father's secret, Miss Winston remained loyal to him.
Like Blight, Miss Winston made no appearances outside the first season of Batman Beyond. In the tie-in comic Batman Beyond #8, Paxton Powers orders Miss Winston's death, because she knew too much. She survived, and became the vigilante Vendetta. Being in Derek Powers' proximity for months had infected her with his radiation, and it made her stronger than most men.
She sought revenge against Blight's enemies—namely, Batman and Paxton—because she had secretly loved him, and sacrificed her own well-being for Wayne-Powers. She caused a major financial setback for Paxton by choosing targets that lay outside Wayne-Powers' grasp, but no-one died.