(Blue Beetle Comics 004, 1940)
It’s fairly unsupported right now as the only other example of a crossdressing villain so far is the Coin, but trust me when I say that an older woman adopting a younger male identity for crime is a comparative rarity as compared to the opposite. I may find myself compelled to note all of the times that non-super gangster types do it, just to lend weight to my claims.
Anyway, the Black-Robed Man. Runs a gang out of a house that is technically owned by her niece, which is how the Blue Beetle gets involved, helping the damsel who is being run out of her home by dastards.