Karel,
I guess I'll have to re-view the movie. However, I will say that I think women would be more inclined to root for Mildred rather than Dixon because she has to contend with a common situation women can identify with: not being taken seriously enough by men.
Also, women demanding justice for the murder of their daughters is a primal motif, an archetypal theme that goes back to Greek mythology and tragedy. (See the Oresteia, Aeschylus' magnificent trilogy on revenge and reconciliation.)
I grant you that working out a strong hook for marketing purposes may not be reducible to a formula. But I think there are some key questions that can be asked to stimulate and guide the brainstorming process. Another thread, perhaps, for another occasion.
Regards and thanks again for providing this vital service to aspiring writers.