Green’s Dictionary of Slang

1. (UK society) clandestinely adulterous.

1899

Daily Tel. 5 Aug. in Ware (1909) 209/2: There are plenty of ladies living, as all their world knows, lives which are generally called ‘risky’, who are personally most scrupulous in observing all the minor conventionalities.

2. (W.I.) flirtatious, bold, cheeky.

1912		C. McKay ‘Disillusioned’ Constab Ballads 45: Will you leave me, heartless Dan, / For a risky to’n woman? [Ibid.] 90: risky: flirty.
1916		‘Recruiting Song’ in C.H. Ward-Jackson Airman’s Song Book (1945) 9: The fellows they were ‘risky,’ they smoked but De Reszke.