Mockingbird's Song (Heartsong Presents)

is book #145 of the Heartsong Presents line.
==Book Description==
Who is the real Martha? — Sturdy, dependable Martha Hollins has always done exactly what's expected of her. But when she accepts a position as an interpretive guide at the National Seashore installation on Cape Cod, "Muffie" deep-sixes her former dull lifestyle. — When her vivacious roommate sets her up with a handsome, life of the party lifeguard, Muffie knows she's in the fast lane. Yet aspects of this fun-loving life--particularly the heavy drinking--make her uncomfortable and she finds herself drawn to the more staid Professor Adam Stowe. But how typical of Martha!
Should Martha admit her real feelings, or should she go along with her new friends, just for one summer? Will Martha rediscover the faith from her past, the faith of Adam, before tragedy strikes?
(Description from paperbackswap.com)