Mina appears in Ch. 3. When the Colossal Titan appears outside Trost District, the burst of steam from its body knocks a number of trainees off the Wall. She follows when Eren instructs the other trainees to attack the Colossal Titan. After the second attack of the Colossal Titan, she was assigned to the middle guard along with Eren Yeager and Armin Arlert. Initially tasked with working under the training corps, they eventually were incorporated into the front guard due to the number of titans. Catching the group unaware, a titan lunged at the roof top they were standing on.
When Eren was talking about how killing titans that got in Trost District will get their rank up high, she joined him indicating that she is also signing up for Scouting Legion.
After Eren's leg got bitten off by one of the titans, She and the other two tries to kill the titan that is responible for biting off Eren's leg. However, her Three Dimensional Maneuver Gear's wire was caught by titan's hand and was knocked over to the wall. When she found out where she was, it was too late for her to escape. She was caught by another titan and her face got bitten off.
Attack on Titan (Shingeki no Kyojin) deals with some very heavy and adult material including fear, betrayal, and, above all, death. With such difficult themes, it's sometimes easy to lose sight of the "sweeter" aspects. Some of the boys and girls we meet in this show are pure eye candy!