While I can't discount your wife's explanation, I would investigate further. Though not a likely explanation for most of the behavior, it would be sensible to check for a vitamin/mineral deficiency. Her pediatrician can arrange for the lab work to do this. Another line of inquiry should be around sensory integration functioning. The proper discipline to evaluate in this area is Occupational Therapy. Third, it would be prudent to arrange an evaluation with a pediatric menatl health professional, such as a clinical psychologist, psychiatristy or clinical social worker. Her problems with impulse control suggest Impulse Control Disorder, and certainly her social skills are impaired. It may be that a combination of medication and social skills group will ultimately be a sensible intervention plan.
Is your child on medication? The symptoms you described are almost identical to those our child suffered when the medication (prozac) dosage was too high and increased too rapidly. The psychiatrist termed the condition "disinhibition". After a painful withdrawal (approximately a month), all negative behaviours disappeared. By the way, our child suffers from several mental health issues. I wish you the best -