Ring of Fire — Heather Huffman

When rare, violet-gray diamonds are discovered at Alexandra McAlister's clean-energy research site on a small South Pacific island, the reclusive scientist suddenly finds herself plagued by greedy gem hunters. To make matters worse, the island's government is threatening to revoke her permits so they can capitalize on the find. 

Fresh from a confrontation with an annoyingly attractive government official, Alex happens upon a girl in danger. Instinct takes over and she rescues the girl, only to find out she is the island's princess, and the annoying official is her guardian, Daniel! 

Alex finds herself thrust into a situation where she has to protect not only her life's work, but also her life itself and that of the precocious teenage princess she grows to love. Daniel appears to be their only chance at survival - if they can learn to get along. Undercover and acting the part of a loving family, they work to find out who is pursuing them and what it is they're after, only to realize their relationship may not be an act after all.