As Jen walked into the cabin, a walker without a jaw grabbed onto her leg and pulled her down, it was going to bite her, but it would be harder to do since it had to push it up to its upper jaw to break the skin, on the walkers back is a small backpack. Since Jen had neglected to smear the guts on her legs, the walker recognized her as human.
(( Here's where you could do whatever you want, but there are things that might be better than others, you could try and axe the walker in the head, but it might get stuck, you could try and chop the walker's arm off, but it would still be alive, or you could call for help. You don't have to do any of those choices, but please be realistic.))