according to the timeline:
Day +83
[16]
- The group reconvenes at the freeway where they originally waited for Sophia. They head east until Rick's SUV runs out of gas. They decide to set up a camp and look for more gas in the morning. Rick tells the group what Jenner at the CDC whispered to him - that everyone is already infected. (TS-19) (Beside the Dying Fire) He also admits to Lori that he killed Shane.
- Elsewhere, Andrea is fighting off walkers when Michonne saves her from a walker that had her pinned on the ground. (Beside the Dying Fire)
- That night, Rick's group is at the fire when they hear a branch snap. The group begin to want either to leave or search out any walkers. Rick uses this event as an opportunity to lay down the rules under his leadership. In the background looms a large prison-like structure. (Beside the Dying Fire)
so at the point they left the farm... it'd only been 83 days since the shyt even started... so she wasn't even out there 3 months
couple that with she told the story of her being in a zombie refugee camp when her family was killed, so she wasn't outside from day 1 either