With their hair beginning to fall out and their skin rotting away, they had a huge fight. When the group at Kiddie Kingdom was attacked, Fran turned on the mist sprayers, spraying irradiated water in the air and effectively ending the attack. She and her boyfriend eventually made up after this event.
After most on the group had died or turned into feral ghouls from radiation exposure, her sanity remained. Eventually she was locked up in a house by Oswald and Dean because she lost her sanity too.