Perhaps she did check The Governor's truck, found no keys and sabotaged it. Then she ran to the prison with, unbeknownst to her, the Governor close behind - hence no noisy truck noise to notice - she gets in sight of the prison and... who among us has not upon finally finding our objective stopped a moment to drink it in? Then, a second hand this episode comes up behind her and, without an annoying tree in the way, pulls her down out of sight.
So close... It reminded me of the scene in Mission to Mars when the teather line is just inches too short to rescue Timothy Robbins