Mrs B's mot would certainly not have been understood in the America of the 1920s, when a bimbo could be a man and a tough one at that. Dashiell Hammett had his characters use it in this way. Raymond Chandler applied it to men in the 1930s, then to women in the 1940s, but not rudely: a bimbo might be simply a girlfriend. She could also be a prostitute, which reminds me of the old Liverpudlian habit of calling the girlfriend "me tart", no offence.
Bimbo comes from the Italian for "child", the masculine inflexion suggesting a boy. In the end American English made no such distinction; meanwhile grown-up Americans of both sexes call their partners "baby". But the "tough guy" meaning is a puzzle. Wentworth and Flexner in their much-consulted Dictionary of American Slang of 1967, thought they had the answer: back in the 1830s bimbo was a word for "a kind of blow or punch with the fist" and "this meaning [the tough one] seems to have derived from the earlier meaning". It sounds impressive. They name as their authority Sir William Craigie's four-volume Dictionary of American English of 1938, which did define bimbo as having once meant "a kind of punch..." but if they had read on they would have found that it added "...made of brandy and sugar" - Sir William was talking about a drink. American recruits in the Second World War were sometimes called bimbos, but probably only because they were thought childishly raw.