We know from The Force Awakens opening crawl that Leia is “desperately” looking for Luke - hence the mission to find the map.
Once the pieces come together, why doesn’t Leia accompany Rey in the journey to persuade Luke to come out of hiding? From the preceding events, in addition to the danger involved in getting the complete map in the first place, one would think Leia would be eager to see her brother. She was so desperate to find him in the first place - now that the path to him is clear, why does she trust a girl she just met to go to him alone with Chewie and R2-D2 and bring him back?