Seagrass Pier, Hope Beach Series by Colleen Coble and published by Thomas Nelson.
One season, Erin Summerall contracted a virus that damaged her heart to the point that she required a transplant to live. She was blessed to have a matching donor, but something very strange started happening to her, almost as if she took on the personality of the heart donor. Her tastes changed in small and large ways, but most strange of all, were her "memories" of a murder she had never witnessed, but could give clear details of the scenes and location to the disbelieving police officer.
Unfortunately, her revelation exposed her as a "witness" who made her fear for both her mother and her daughter's life. To hide, she fled to a remote cottage that is only accessible by boat, on Hope Beach. Knowing she can trust Mark Everton with her life, she pleas for her. There's a catch; she never told Mark about being pregnant their daughter before she left the island. How can she bring the killer to justice and reconcile herself and Marc to the "new" Erin?