The Other Room by Katherine Hastings

Will an unwanted roommate turn into an unexpected romance?
Even though Jo is furious with her ex-best friend Matt, she takes pity on him when he ends up homeless. The two frenemies and her nasty cat squeeze into the tiny beachfront cabin she scored on the Door County waterfront. But as mad as she is at him for his betrayal, staying that way proves more difficult than she thought when his charms start wearing down her armor.
It’s more than the walls between their rooms that separate Jo from Matt. He’s desperate to gain her forgiveness, and soon he’s desperate for a lot more. The passion igniting between them threatens to burn their little cabin down.
As Matt tries to break down the walls between them, Jo struggles to deny her feelings for him… feelings that are anything but anger.