Living on the generational ship required discipline. Discipline with maintenance and especially discipline with safety. Hull breaches were constant, something not unforeseen on a ship constructed thousands of Earth-years ago. When a bulkhead gave out, the siren sounded, and it would be up to whomever could reach the airlock first to close it, no matter who was left behind. To wait for a loved one would only condemn others to die. More to the point, were you to fail, someone else would just be at the next airlock to sacrifice you instead. It was the tragic reality of the hard life of deep space.
That being said, once Abigail ejected her third brother into space, her parents began to suspect she wasn’t all that sorry about it.