This has been bugging me for a while.

Regardless of how Dany ends up getting her ships, if/when she eventually leaves for Westeros, what will happen with Slaver's Bay? Maybe I am missing something, but I can't see a way for her to leave and not have the Masters take over again. She has spent so much time and effort trying to end slavery and prevent the Masters from gaining control again. If she leaves with her army, what is to stop them from going back to how things were? There is the possibility that she could leave a portion of her army behind, but is that smart? She will most likely need a large force to take the Seven Kingdoms, so it wouldn't make sense to not take all available soldiers.

If she just up and leaves, the whole time spent in Slaver's Bay is almost a waste. What am I missing? How does she leave and still prevent slavery from returning?