I don't know Faye Gunn, but from a quick Google, she appears to be a woman - so not a good choice for Ian McShane.
Faye Gunn is not some young bimbo. She's sort of a female equivalent of Dickens' "Fagin" (Oliver Twist), so why couldn't she played by a man (in drag)?
Most images I get from Google are of a young looking woman (albeit with white hair)
I'm assuming those are all maybe New52 images, not from when she was originally created (back in 1987).
Also, for issue #1 of Red Hood & the Outlaws under Rebirth, they showed a more "mature"-looking version again.