Presumably Leia was up for becoming an early pupil of Luke. Frustrated at the continued fragility of Galactic peace and already possessing a Skywalker choking streak she begins to dabble in the dark side in the hope of uniting the Galaxy under a strong leader. The deeper she dabbled the darker the path. Using the Snoke persona she turned her son when he joined Luke’s classes and he gathered a group around him who killed the other Jedi and to avoid having to kill his beloved sister and nephew Luke hid in shame and fear for the child he left behind. Using the Resistance and The First Order Leia has been trying to find her brother. That is why the partial map held by Renn and Leia is the same. SNOKE to Renn : I am your mother