One or two girls? That should add flavour (8)

I believe the answer is:

rosemary

This clue is a double definition.

'one or two girls?' is the first definition.
(Rose and Mary or just Rosemary)

'that should add flavour' is the second definition.
(herb)

(Other definitions for rosemary that I've seen before include "Plant" , "Aromatic shrub" , "Fragrant evergreen shrub used in cooking" , "such seasons" , "Herb - girl's name" .)

I've seen this clue in The Telegraph.

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