Fated to Mate by Anne Conley

Kelli and Chase grew up together and know the rules: when he comes of age, he’s got to choose a shifter to bond with, period. And Kelli’s not a shifter. There isn’t any way around biology.
But chemistry is something else entirely, and Kelli did the one thing she never thought she could do—move to the city to escape it. Her feelings left her no other choice. It was the only way she could see for Chase to follow his shifter destiny.
Now, Chase is getting a divorce from the shifter who was supposed to be his bonded mate, and some crazy friend of his Grandma is telling him he can bond with humans. It’s not the way things have always been in their little shifter community, but Geri Wilder keeps telling him they’ve been doing things backward.

Now that Kelli is back, Chase is angry and confused, seeing the truth of the mistakes they’ve made. However, Kelli is only in town to plan her wedding.

To someone else.