There's not much to say. After the incident with the Core, Nill was... bad. Left Terezi, regardless of Terezi's thoughts on the matter and regardless of the raging headache and the nose she couldn't get to stop bleeding after she crushed the core. Threw up the last of whatever was in her stomach, too. Then the rest until she died.

Instead of really offering a response Nill reaches for her spiked coffee and takes a long, healthy sip, enough to down almost a third of the drink.

All things considered, it's probably enough of a response.