Mer-charmer

the long version

"Her sister is a fairy keeper ... her best friends are merfolk ... and all she does is dishes and housework. Fourteen-year-old Pohebe Quinn is surrounded by magic, but she can't muster any of her own. When Phoebe finds out a terrible sea creature is awakening that preys upon the peace-loving merfolk, she becomes determined to help them, even though it means going with Tristan and Mina to their home deep in the sea."--Back cover