I think the series used Genda as a composit of a couple or few people. Glenda had been on record calling the cops for months before his arrest. Which started with the cops and the 14 year old.
But the scene where she was offered the sandwich was a different neighbor. She lived across the hall and had indeed ate meat that Dahmer gave her.
So in the series, to make story telling easier and more poignant, the made experiences from probably multiple neighbors and Glenda and rolled them into one