This book is really by Cynthia Felice AND Connie Willis, despite what Goodreads lists above. Deza is a con artist trying to pass herself off as a water witch, someone with a supernatural ability to detect, control, and communicate through water, which is a big deal on this dry, poisonous planet. But her con isn't going well as her father has just died and his spirit has been transmuted into this goat-like creature that is sending her telepathic messages.
BTW, I liked this book about 100 times more than Light Raid by the same authors, and yet I give them both four stars. Go figure.