Tanya Huff 
Wild Ways: An Enchantment Emporium Novel 

Charlotte Gale is a Wild Power, but there’s nothing wild about the life she is living. When her meddlesome aunts start interfering, Charlie ditches her cousin Allie and their grandmother’s Enchantment Emporium and joins a Celtic rock band on the summer festival circuit. All Charlie wants to do is play music and have a good time, but she soon becomes embroiled in a fight between an extended family of Selkies and an unscrupulous oil company willing to employ the most horrific means possible to get what they want, including one of the Gale aunts…