Emma Richmond

The heroine is dragged into chaufering the hero & his young son.  The hero is in a battle with his soon-to-be ex-wife.  The hero/heroine get stranded together over night, and the ex-wife slyly discovers that info and uses it against him to create a scandal in the divorce proceedings.  The hero thinks the heroine conspired against him with the ex to hurt his chance of custody of his son, and he blames her and yells at her.  She wants to explain, and finally he starts to see sense and think that she's telling the truth.  They need to verbally arm wrestle their way through the myriad of issues they have, and they wrangle a solid understanding and start their relationship on good footing (by the end of the book).  You get the impression they have talked through a lot of their issues, in a natural progression.