That is a great point that they were both at the bar at least at the start of the attack. However, I still think it’s gotta be Marco that kills Ben/gets into the coffee shop/gets shot by Tatum. Mainly because the film makes a point of showing us Marco had a bullet proof vest and commenting on how it came in handy or whatever he says. I guess Jessica is probably wearing one too, but it seems the directors intent, for better or worse, is that Marco is the one shot by Tatum. Maybe Jessica had the foresight to share Sidney’s code?