Deadly Gamble by Connie Shelton is the first book of the Charlie Parker mystery series.
Charlie Parker has a PI firm with her brother, but as the accountant, she neither has the license nor the credentials to work on investigative work. That doesn't deter her when her brother is out of town and the woman (and former best friend) who "stole" her fiance asks for help locating an expensive watch. When the woman is accused of murder Charlie jumps in and decides to investigate on her own.
Deadly Gamble was a light read in the form of the Kinsey Millhone series, but set in New Mexico. I've read a few of Connie Shelton's books and she has several free for Kindle at the moment.