Get your facts straight. First off, she tried to get off the case but couldn’t. She was obligated to defend the man, and all criminals have a right to legal representation.
She didn’t laugh about getting him off and in fact some of her laughter can be attributed to the fact that she said she’s lost all faith in polygraphs because he passed it.
It sucks to have to defend horrible people, but this is what lawyers sign up for when they become lawyers. Just because she laughed about some of the circumstances of the case after the fact, doesn’t mean she didn’t find what her client did completely deplorable (see what I did there?). She had a duty to defend him, whether she liked it or not.