Her voting changed incredibly quickly (9)

I believe the answer is:

overnight

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'quickly' is the definition.
(eg something might change overnight)

'her voting changed' is the wordplay.
'changed' indicates an anagram.
'her'+'voting'='hervoting'
'hervoting' is an anagram of 'OVERNIGHT'.

'incredibly' is the link.
I am not very happy about this link. It may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for overnight that I've seen before include "darkness" , "Lightning" , "until tomorrow" , "sudden" , "Extending from dusk to dawn" .)

I've seen this clue in The Times.

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