424 "Mastermind"
Lightfoot on April 1, 2021
This isn't totally out of left field, I had left several hints. Annie said her Mom's family had psychic powers once, and if Mastermind's appearance didn't happen on a page with so much environmental coloring, you'd see she had the same skin and hair color as Annie.
Jessica has taken so long to appear as regular because I didn't want many B-Class heroes early in the comic. I was trying to save them until Annie and Tabitha were on the edge of becoming a C-Class team (with Charlotte) and going out as regular superheroes.