Ok, let me see if I get this rosecarmel... Your friend is unhappy in her marriage, and so, among other things, no longer wants sex with her husband. The whole relationship "exhausts" her, but she's settling for just stopping he sex because she doens't want to lose him.
If she were deliberately withholding - or providing - sex to get something specific, I would say that was manipulation. But, as others have said, since it's just a matter of her not wanting sex because he is emotionally abusive, etc. then tha's not manipulation. In fact, I would say, she's trying to protect herself from further emotional manipulation or maybe expressing her unhappiness in a non-verbal way. Or perhaps she's punishing him for his abusive behavior by withholding sex, which I wouldn't blame her for. Or maybe she just doesn't feel all lovey-dovey after being verbally abused. I know I wouldn't.
What concerns me more is that she hasn't sought counseling or doesn't just leave him. Why is she afraid to lose someone who has been so cruel to her? I get her refraining from sex, but, imo, it's a poor substitute for getting away from him, altogether, and seeking a happier life. Has she given any thought to divorce? I hope so.