Who is Gabrielle Ashe from Deception Point and what is their importance?

Gabrielle is Senator Sexton's primary aide and adviser to his campaign. She is in her early twenties and is beguiled by Sexton's charisma and politics. Through the course of the story, she slowly begins to realize that he is egotistical and self-serving. After having a one-night affair with him, she is surprised and a little disturbed at his exceptional ability to lie and turn the tables on others. Gabrielle also wants to believe the best about her candidate. When shown evidence of his having taken bribes and illegal funding from the private space agencies, she at first refuses to believe it. Slowly, as the evidence mounts, she begins to believe that the Senator is capable of such a thing.