Fall in love with a mermaid? Have trauma hating herself for falling in love with what she considers to be one of the reasons her parents died? Slow dramatic resolution through love of her mermaid partner? Just shooting quick ideas here.
Plaza's, national landmark's, places where people gather, and potentially hold festival's and rally's at. A couple apartment complex's could hold 100 people depending on the size of the building and if you warp in some neighboring complex's.
It's good so far, havn't really seen any glaring mistakes. Don't know who the MC or what the plot is yet, but that will come later. Keep writing, need some more chapters to really tell you what I think of it.