It's Lili De Neuve's turn for the spotlight in Secret Six 6 (Feb/March 1969), by Bridwell, Gill and Sparling.
The story opens with a woman being killed at Lili's spa, leaving her looking like the killer. She calls in the rest of the Secret Six to aid her, and explains to them that the dead woman is the one who framed her years before for murder. We learn that Lili had been an actress on her way down, and the killer was being a total bitch to her, before framing her for killing her lover. Mockingbird bribed a man, using King Savage as his go-between, to provide Lili an alibi and save her from the guillotine.
The team determines, through politely (or not) questioning a hoodlum the dead woman was associated with, that she had been blackmailing a guy, the most likely one to have killed her.
Crimson then goes into action to seduce the guy, and drugs him. Lili makes herself up to look like the dead woman, and then confronts him.
The guy is all freaked out and confesses to the murder, and then the lights go up, and he discovers he is standing on the stage of a theatre, in front of a packed house. I always wondered who made up this audience, how they were enlisted to take part, and what they thought they were really watching.
As the series goes on, it sort of passively keeps knocking out potential suspects for Mockingbird. Lili could not be Mockingbird, because she had no reason to adopt that identity before she was framed, and she was working for Mockingbird before Crimson was, so that removes her as well.