Maisie Undercover: Shadow Boxer (2006)

When a female boxer refuses to throw a fight, she is murdered. Detective Dan Calloway rules the death a suicide, but when the boyfriend Bronson Cole wants further investigation, Calloway sends him to his ex-wife Maisie Calloway, a beautiful ex-cop and bar owner who moonlights as a private detective. Maisie takes the case, going undercover as a boxer with ex-champ Cole as her trainer, and quickly becomes a favorite of Guy Felix, the sleazy promoter of a illegal underground fight club who rigs the fights and pimps out the female boxers for his own profit. However, Maisie's investigation is complicated when Cole gets involved with another female boxer and when her ex-husband shows up appearing to have gone corrupt.