Been a while since I saw Plus, but, I always assumed Sharon always used some kind of trance inducing hypno stuff even for her regular concerts. All for the purpose off "showing the audience a good time" and be a commercial success really. You notice the audience in the concert in ep 2, who are probably used to it, more or less instantly enter some happy trance, while Isamu, who's at his first time at a Sharon concert is looking at them weirdly. Though later, even he begins to act more "Wow, this is pretty trippy stuff".
At first I thought it was tied to those ticket/bracelet things they get when they enter concert hall, but since not everyone who got hypnotized at Sharon's last concert on earth had them (did anyone even?) I guess they were mostly just used for 'measuring the excitement level' of the audience. So I guess she was doing it on her own so to say. Perhaps when she got that bio-chip and became her 'own' this ability intensfied?