Green’s Dictionary of Slang

a general excl., lit. there’s a woman with a lot of hair.

1900		‘Doss Chiderdoss’ ‘A Baffled Orator’ Sporting Times 2 June 1/4: The ‘tickler’ damsel fair, / As on Mr. P.’s bald cranium she fixed a saucy stare, / Left no room for doubt by yelling out the shrill reply, ‘There’s hair!’ / Which completely put the kybosh on the orator.
1928		M.C. Sharpe Chicago May (1929) 108: The English had a slang expression, ‘There’s hair,’ similar to our present American slang, ‘So’s your old man,’ or ‘For crying out loud.’.