There have been several unbelievably interesting studies on Marijuana and its components done recently, with quite unexpected results. Of course, many were performed in adolescents, a group of huge concern when it comes to THC.
Everything might play a role in the outcome, the potency, the length of use, but also, individual predisposition. Perhaps pre-existing mental illness, for which, ironically, marijuana might be used to self-medicate, plays a role. One can expect high-percent THC formulations and the length of use to be important factors, but the response is still very individual. A study linking synthetic marijuana to psychosis was done about 10 years ago, and I think it might have been one of the first ones.
However, we can not use the results of any study to interpret what happened in that case, as there are too many factors into play, and probably, on both sides. It still seems to be the "road rage", and "road vigilantes", and "stand your ground" to me, and plus, wasn't she pregnant? Pregnancy itself is a complex factor here, as well as availability of prenatal care. I am just thinking of how unsafe their neighborhood was on that day.