V.W.
Consequences.
When she lies to you, you give her the same consequences you would had her brother NOT been the one to tell her it is ok. Same thing with disrespect.
And the same goes for him... he lies, you give him appropriate consequences. He disrespects you, you give consequences. If you want to include him telling her to lie to you under "disrespect" then go for it.
You can't rationalize with her that she shouldn't listen to her brother. You can only teach her that there ARE consequences to her behavior. If she chooses to lie, she get the associated consequences. If she chooses to be disrespectful, she gets the associated consequences. Eventually, she will figure out that those consequences aren't what she wants to live with... She might even start to ignore her brother's "suggestions" when she realizes that he might be WANTING to get her in trouble so he can watch her suffer. Yes, boys DO do things like THAT. Particularly, if he has some reason to be jealous of your daughter. And I'm guessing since they are half-sibs and he is just now coming to live with you, that he does have reasons to be jealous... at least in his mind.