I think it is unlikely that a child would become withdrawn, underweight and sensitive to stimuli from eating too many supplements.
It sounds from the story that very likely 'Mara' had ME/CFS. The authors claim that she did not fit the diagnosis but they describe her as if she has it. If she didn't have it, it is unclear what was wrong with her.
This is not MBP to my mind but I think it raises important questions about what effects interpersonal relations might have on a child with ME/CFS, including in terms of prolonging the period of disability.
The authors' analysis fails to shed any light and merely confirms their prior pigeon-hole thinking. But the case may nevertheless be instructive.