This sounds very much like my daughter with autism. Perhaps you could direct mom's attention to a news story or some neutral source about autism, and gently ask if she's spoken about her child's development with her doctor. I
Sets and Reps that I Respond toby
and error, I noticed I respond best to a certain range of reps and certain number of sets. Not all the time... reps per set. I also noticed that I respond to explosive movements: hang cleans, kettlebell swings...