She has to be careful not to push him so far though that he kills her accidentally in a rage. She senses he’s operating on a hair-thin trigger. But based on the short duration and generally low level of overall pain, she guesses he’s still in control, at least for now. And luckily for her, so was she. She was, after all, no stranger to this curse. Besides, he certainly didn't have the same hatred raging through his body. His curse did quite have the *pop* that Bellatrix’s did.