Sara Dashwood has always been afraid of rejection. Sara did not have many friends because of her fear

Sara’s roommate Susan has always used people and she did not care about hurting anyone.
Susan starts dating a soldier named Charles. Charles leaves for active duty. Susan agrees to write to him, but she broke her promise.
Sara feels bad for Charles and starts writing to him. Sara lets Charles believe that Susan is writing to him.
When Charles learns the truth, he starts looking for the woman that saved him.