Probably a contemporary Harlequin - H has affair with orphan h, but leaves her for her cousin

70’s setting maybe?  The heroine was brought up by aunt and uncle and had a career.  She slept with the H, but once he met her cousin he decided he’d prefer a more traditional / virginal spouse.  Dumped the heroine, married the cousin and heroine moves away as she’s pregnant.  She runs to grandmother-maybe?  

Cousin dies and “Hero” comes to find her. Think they marry.  What can I say...I’m in a mood to read “train wrecks” and just can’t recall this title.