Bookie's plea to rich old girl? (7)

I believe the answer is:

dowager

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'rich old girl?' is the definition.
(I've seen this before)

I cannot understand how the remainder of the clue works.

(Other definitions for dowager that I've seen before include "One of 16 [OLD GIRLS]" , "wealthy widow" , "Widow, imposing elderly woman" , "Wordage (anag.)" , "Dignified (or wealthy) elderly woman" .)

I've seen this clue in The Sun.

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