Most concerts are dimly lit. The ones without pro light show, follow spots, moving yokes, par cans, are the worst. I can only advise big aperture (F/2.0 or bigger), as high an ISO as you can tolerate to get the shutter speed you need. From the looks of your shots, she was not overly athletic in her performance. So it could be possible to shoot at 1/30th with up to say a 105mm f/2.0 with good technique to get your ISO down to a manageable level. Maybe 640-800? Available light concerts are a challenge in anyones book. With practice, we all do better and finally get results we are really proud of.