A substitute teacher is usually a well-trained licensed teacher who is only temporarily filling in for the regular permanent contract teacher's absence. I have known fully degreed and licensed substitutes who make a career out of this, at excellent wages. Don't sell this way of earning a living short. It has many options that the tenured school employee does not.
If I was placing a bet on this situation after reading the summary, I would put my money on the substitute having done exactly the right thing, in view that the mother has never trained her daughter to be obedient when given a command by a legitimate authority.
Perhaps you can learn from this parable, too?
You can't alter a baby's behavior (or a dog's or horse's) by reasoning with it, can you?
I was not selling substitute teachers short. I'm simply saying she may not have had the LD courses that are often required when teaching special needs students. As for "done exactly the right thing", I seriously doubt that it's prescribed behavior to wash a students mouth out with soap.