Green’s Dictionary of Slang

betty lea n.

also betty lee

[rhy. sl.]

tea.

1960, 1975		Wentworth & Flexner DAS 647/3: Betty Lee – tea.
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.
1984		Partridge DSUE (8th edn) 73/1: first recorded [...] in 1949.