As far as the way the cops handled the Aug. 12 stop -- since everyone wants to just blame those cops for what happened later -- it's VERY possible that they saved her from being murdered THEN by separating them for the night. A "mandatory" arresting policy would have resulted in Gabby being arrested that day based on how their side-of-the-road investigation was shaping up, not Brian.
But if that 9-1-1 call had not happened, if those cops never made that stop interrupting whatever crisis was happening between that couple, it's VERY possible that things would have continued to escalate on THAT day as apparently they did 2 weeks later.