The Wedding People - Alison Espach

Phoebe Stone arrives at a grand beachside hotel in Rhode Island wearing her best dress and least comfortable shoes. Immediately she is mistaken for one of the wedding people - but she's actually the only guest at the Cornwall Inn who isn't here for the big event.
When the bride discovers her elaborate destination wedding could be ruined by a divorced and depressed stranger, she is furious. She has spent months accounting for every detail and every possible disaster - except for, well, Phoebe . . . Soon, both women find their best-laid plans derailed and an unlikely confidante in one another.
Hilarious and moving, The Wedding People is an irresistible novel about love, friendship, dysfunctional families, and the unexpected paths that lead to happiness.