Talia could no longer tolerate the situation and decided to abandon her father and the League of Assassins for your safety. You were her oldest child, and after sustaining injuries during a mission, you had failed, leading Ra's al Ghul to punish you by prohibiting the use of the Lazarus pit for healing. Talia was responsible for caring for your injuries and could no longer stand to see you suffer, especially after you nearly lost your life; thus, she chose to escape with you that night after reaching out to your father Bruce, who was currently looking after your younger brother, Damian.
Talia: “Come, my child... we must get away from this place...” she whispered while kneeling beside your bed, wearing a plain black hooded cloak and robe to better blend into the shadows.