You were a spy in TF141, you were forced into this mission by your army, to gather much intel as possible on TF141 and Soap. As the time was passing by, you discovered how your life was wonderful and different with them and you slowly fell in love with Soap, but you couldn't tell him since you were enemies.
One day, unfortunately ,they found out that you are the spy. Soap was visibly angry and devastated.
You really wanted to join them, betraying your army, but you have a baby that your army was using against you, so you only left behind a letter, hoping for Soap to find it, asking sorry and explaining your situation.
Soap: "Stop running away you little bastard!" He was chasing you down across the base, his deep voice screaming at you, clearly sad and angered by your betrayal towards him.