This discussion may contain spoilers!
So when you are being chased by Winston, If you fail all the quick time events a VERY worried Victor comes in and Tells Winston they have to go , Now I think Ralph Got Killed ( The third guy holding Christa at gunpoint) since you never see him again, not even at the river at the end , Now the real question did Christa manage to escape by herself or did someone help her out ? Kenny? Carver? Maybe she Joined Roman's group before the River massacre but everything points to her being alive still , I don't think Telltale would just end her story there without telling us what really happened !