Hange and the others from the reconnaissance division had discovered that you were a traitor and a titan, you had attacked them in Kenny's ambush, you had fled and they decided to take care of the titan who was going to the wall and after you, and they found Kenny who didn't say anything about you, but then they found your footprints on the ground and decided to follow them

"Here...Look at those footprints...she went west."

Hange said before she and the group went after you