post #2827984 post #2776516
Sallie May is Millie's younger sister and one of the two daughters of Lin and Joe.
And she is a transgender woman.
This is also implied in her design, as her horns have thicker stripes, which have only been generally seen on the male Imps in the show. Some of the merchandise featuring her in a swimsuit also show her having a clearly visible bulge, suggesting her having a penis.