“Girl Violence,” the third and most recent album by the singer and multi-instrumentalist Mikaela Straus, a.k.a. King Princess, ushered in a new era for her experiments in sonically fluid sapphic pop. If “1950,” her breakout single, from 2018, was emblematic of a vintage musical matrix that she has spent much of her career so far riffing on, “Girl Violence” longs to synthesize those sounds into something more peerless and forward-thinking. Straus, equal parts pop agitator and quirked-up rock star, wants to add more ferocity to songs of the queer canon. She brought her learn-as-you-go energy to a performance and talk with the staff writer Amanda Petrusich at the twenty-seventh annual New Yorker Festival.