Z for Zachariah (2015)

In the wake of a nuclear war, a young woman survives on her own, fearing she may actually be the proverbial last woman on earth, until she discovers the most astonishing sight of her life: another human being. A distraught scientist, he’s nearly been driven mad by radiation exposure and his desperate search for others. A fragile, imperative strand of trust connects them. But when a stranger enters the valley, their precarious bond begins to unravel.

Source: TMDb