Shes out of breath (6)

I believe the answer is:

bertha

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'shes out' is the definition.
I can't tell whether this definition defines the answer.

'of breath' is the wordplay.
'of' indicates an anagram (the answer comes from or 'of' the letters).
'breath' is an anagram of 'BERTHA'.

Can you help me to learn more?

(Other definitions for bertha that I've seen before include "The bar (anag.)" , "Female name; Big -, World War one German howitzer" , "big woman?" , "collar" , "Woman's name" .)

I've seen this clue in The Irish Independent.

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