Green’s Dictionary of Slang

a thief who robs innocent pedestrians who have been deliberately tripped up by a confederate; often a woman who preys on drunken seamen.

1865		Leaves from Diary of Celebrated Burglar 138/2: Til [...] was a tall, stout tripper, who made a living by rambling the streets and ‘kidding blokes’ to her ‘dossing crib.’.
1887		Daily Chronicle 18 Nov. n.p.: [...] tripper[s]-up [...] a man who trips you up and robs you. If you make a noise they jump on you [F&H].
1889		Clarkson & Richardson Police! 348: ‘Coshers’ and ‘trippers’ [...] are vile men and women.