Green’s Dictionary of Slang

(Aus.) a phr. used to reject offers of assistance, don’t worry, don’t fuss, everything will be fine in the end.

1938		X. Herbert Capricornia (1939) 273: At last he crawled from under the engine, spanner in hand, and dashing sweat from his forehead, said to the gathering, ‘That’s the lot. She’s right.’.
1945		Argus (Melbourne) 3 Apr. 2/5: Australians use the word ‘she’ instead of ‘it’ to quite a remarkable degree. If a group of you are putting up a tent, and it is fixed so that it will satisfy, then the corret announcement of satisfaction is: She’ll be right. There is no similar usage in ordinary English.
1947		Argus (Melbourne) 8 Mar. 18s/2: [cartoon caption] She‘s right, fellers.
1951		(con. 1941) E. Lambert Twenty Thousand Thieves 227: ‘She’ll be right, Mum,’ someone else drawled.
1958		F.B. Vickers Though Poppies Grow 76: ‘You’re free until we take a firm order. But bring the permit with you.’ ‘She’s right mate. Thanks a lot.’.
1959		D. Niland Gold in the Streets (1966) 207: ‘Chris, can you lend me a tenner?’ Chris said: ‘Sure, Danno; she’s right.’.
1961		B. Crump Hang On a Minute, Mate (1963) 33: Thanks for the beer, added Jack. She’s right, said the barman.
1963		R. Stow Tourmaline 83: ‘Stay the night with us?’ ‘Ah, she’s right,’ Dave said.
1977		B. Scott My Uncle Arch 80: ‘Need a hand, ‘Arry?’ Good bloke, Mick. ‘She’s right, Mick!’ [AND].
1978		D. Stuart Wedgetail View 21: What d’ y’ reckon, should I drop back a bit an’ put up a smoke, let them know where we are?’ ‘No, she’s right, Col. Davey’s got one going.’ [AND].
1986		R.G. Barrett Godson 233: ‘Would you like a hand?’ ‘No. She’ll be right’.
1988		McGill Dict. of Kiwi Sl. 99/2: she a substitute for ‘it’ in a variety of phrases intended to soothe, such as ‘she’ll be right’ and ‘she’s jake’.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].
2018		G. Gilmore Base Nature [ebook] Davie had once heard him complain that ‘She’ll be right, mate’ was generally a lie.