Nothing is known about the old woman's life before the apocalypse except that she lived in Mexico.
At the Gonzalez Dam, this old woman is among the many people in line waiting to trade supplies for water. After presenting a bag of batteries to the guard, she is granted two liters of water, to which she smiles happily.
Although unseen, it can be presumed she stayed at the Gonzalez Dam and is still alive.
It's unknown what happened to this lady after the dam was exploded. It's possible she was the many people that was killed by the proctor gang or was killed after the dam was destroyed.