A Little Night Murder by Nancy Martin

Nora Blackbird - pregnant at last! - is spending summer afternoons wallowing in the Bucks County pool of her best friend, Lexie Paine, who has just been released from prison. At night, Nora is covering Philadelphia's high-society events for the local newspaper. And this time she doesn't have to look far for a good story.
Next door, a Broadway show is in rehearsal at the estate of Toodles Tuttle, the long-deceased but ever-legendary composer. Reigning over the estate is Toodles's diva widow, Boom Boom. The demanding old broad still rules with an iron fist, and considering the chorus line of enemies she's racked up over the years, her death has been a hotly anticipated event. So imagine everyone's dismay when it's her beloved daughter, Jenny, who drops dead - from a cause that is anything but natural - just as the lights are set to go on for the lucrative new Toodles musical.
Nora's sister Libby, a soon-to-be-grandmother, has gotten herself into a sticky situation, wooed by both a lowly bug exterminator and a cheesecake-loving Broadway impresario. Edgy sister Emma has a dangerous new boyfriend who may jeopardize her show-jumping exploits. And the love of Nora's life, Mick Abruzzo, has been desperate to prevent Nora from meeting the most notorious member of his mobbed-up family - his mother.
Now Nora has to deal with the bump-and-grind of her personal life, and also bring the curtain down on a daring killer - before he forces her to exit stage left, permanently.

This book is part of the "Blackbird Sisters Mystery" series.
Here are some other books from this series: