Complex sentence: She claims that she has an Axis II personality disorder, making her unable to feel and/or express common human emotions like fear or sadness which made her unfit to become a doctor so she joined the U.S Marine Corps.
Split into simpler sentences: She claims that she has an Axis II personality disorder, making her unable to feel and/or express common human emotions like fear or sadness. This made her unfit to become a doctor so she joined the U.S Marine Corps.