Who is Allison Manning from Dead in the Water: A Novel and what is their importance?

Allison Manning is married to Paul Manning, a popular novelist. The couple have been on a year-long yachting trip around the world. However, the trip has ended in St. Marks without Paul Manning. Allison Manning is immediately questioned by the police and charged with murder. Allison claims that Paul died of a heart attack ten days out of the Canary Islands and she threw his body overboard. However, the police have found a diary that seems to suggest that Paul and Allison were not getting along, leading to Allison's desire to kill her husband.