Hannah is a member of the 104th Trainees Squad. Hannah first appears in Ch. 3 walking through Trost District with Eren and Franz. Eren refers to Hannah and Franz as a couple, which they both embarrassedly deny.

Spoiler

In the 5th chapter, Armin finds Hannah in the street attempting to administer CPR to the corpse of Franz. Her efforts to resuscitate him are futile, as he has been bitten in half. Armin advises her to give up and retreat back to Wall Rose; then, unable to bear the carnage any longer, flees. As she has not appeared since, it is unknown whether or not she took his advice and survived or remained and perished.

(Source: Shingeki no Kyojin Wikia)