Can't we all agree that we don't know anything about the characters yet.
So the people saying "A female outlaw leading a gang would really be against source material, do they not care about history?" or "Why can't Rockstar add a female outlaw, are they sexist?" We also can't really make assumptions about the main characters yet. If you look at the original press releases for GTA:San Andreas or RDR, there's no mention of any strong female characters, yet both of those games have the strongest female characters of any big time games (Kendl Johnson and Bonnie McFarland)
He sure does. And if this is a prequel, it might suggest that the 7 people in this photo are not allies or members of the same gang. In RDR, Marston had only known of Rickets through his legend, had never had any real interaction with him prior to the events of RDR IIRC.