Both of their powers change every time a writer farts. In the first season Liv still pretty much was in control after eating someone's brain, the second season she's not in control and do all types of over the top shiat. She barely turns zombies super woman anymore.
shareLiv's resistance to impulses from eaten brain my be fading the longer she is a Zombie.
shareThis is a good point I hadn't thought about. I did notice that she was more over-the-top and seemed to consistently stay in that 'brain' for the whole episode in season 2, but I couldn't figure out why. In season 1, it was more like she took on some of the traits but could regulate it a bit better and was still mostly Liv, unless something triggered a response. It would be interesting to see if there's something to her losing more control over the brains' effects on her.
Go with your heart, buddy. Our brains only screw things up.