My Sister’s Keeper by Mavis Applewater

Nothing is ever easy for policewoman Jenny Jacobs. She just wants to be in love. Sound simple? Well, there's a catch. She wants to be deeply in love with someone who is also deeply in love with her.

Jenny must face the past and the present when she discovers her lover's infidelity and her first love walks back into her life. Her life becomes even more complicated when old feelings surface for her first love -- the woman who broke her heart as a teenager, then entered the church and became 'Sister Rachel'.