Zerchers are not squats. Dumbbells are not part of this program. There are hurdles here that you cannot clear, so the only logical thing to tell you...
Compare the depth on the first sets' early reps with the last set, and you'll see that depth is not consistent. Some of the minor knee wobble is from...
If she trusts you, teach her about the Stress/Recovery/Adaptation cycle, and start her back training with light weights, progressing her like she did...