I've heard MUCH worse than that at live events. At a couple NASCAR races back in the day, even. At least she was in key.
I saw her open for Santana in Hartford back in late '90s / early 2000s. It was horrible. She was incoherent (she seemed angry, but I couldn't make out what the hell she was caterwauling about), the sound was fucked up, and the music just plain sucked.
Then Santana got up there and immediately start spouting political bullshit. I shouted at the top of my lungs, "SHUT THE FUCK UP AND PLAY SOMETHING." He had to hear me, as I shouted it while he had paused. I got a cheer from some of the audience, and booed by others.
I loved Santana's music, but for fuck sake, don't go thinking your audience is there to hear the naive political rantings of an aging, ethereal, pot-head. I think that was the last Santana concert I went to anyway, as I had begun to realize he played almost the exact same set every single time I saw him.