Bookish Belinda by Jo Grafford

Belinda Fairfax has an ax to grind with Colt Branson. She’s been patient — as patient as can be expected by a woman who was jilted at the altar by the only man she’s ever loved. She quietly supported his decision to travel west in search of his missing sister. She wordlessly held her tongue when he and his brother opened a mail-order bride agency — with their one-of-a-kind Gallant Rescuer clause — to help prevent any other would-be brides from suffering the way their sister had suffered.
However, Belinda draws the line at watching Colt’s brother, Jordan, fall in love and marry one of their lovely clientele. For all she knows, Colt may be courting someone, too. She breaks her silence with a letter, delivered to Headstone by the next mail-order bride. When a few months pass with no response, she decides writing isn’t enough. Without the funds to travel west to confront her former affianced, she sees no other choice but to sign one of his blasted bridal agency contracts and send herself to Arizona as a would-be bride!