Guilty of Love — Mildred Colvin

Nicholas Bradshaw had a crush on Julie St. Clair in high school, only she was already taken. When their paths crossed a few years later, they fell in love and married.
The only problem is her old boyfriend, Darrell, who married her best friend, Heather, lives nearby and the two men carry on a frenemy-type competition. Nick knows secrets about Darrell, and he believes his rival still carries a torch for Julie.
Julie Bradshaw takes a job at Darrell's insurance office against Nick's wishes hoping it will keep her truck-driving husband home more with her and their three sons. When Nick is late coming home for Christmas, Julie fears something terrible has happened and tells Heather. He walks in as Darrell is consoling Julie and gets the wrong message. Or is it the right one?
In an attempt to patch things up in their friends' marriage, Heather and Darrel trick Julie and Nick into spending three days together alone in an isolated cabin far from home. Only Heather hasn't counted on needing them to help her at the worst time in her life.