Rosie the Rampager Achievement
Rosie the Rampager20
Arrive at Final Destination with Only Female Survivors
For both of these achievements your last chance to make sure your group is gender specific is directly after you complete Sherwood. It's best that you dismiss them either after leaving Danvers or Polksville, but you still have a chance before Sherwood. Sherwood even provides you a place to grab either the male or a female survivor with either Harrison or Jane (not able to grab both). This of course will make you have to do 2 playthroughs.