In the first Men In Black movie it is made quite clear that K is still in love with
the girl he left behind which he had to abandon to be a Man In Black.
But in MiB he flirts heavily with Agent O, even though the incident with
the girl he left behind must not have been long ago. And J even makes snide remarks about it.
From a narrative point, this plotline makes K look more human in MiB3 and adds a subplot with a love interest, but it completely disregards K's personality from MiB1.
Can it be assumed that the screenwriters just disregarded K's History to have a love interest in MiB3?