She removed the potion from the heat once she was certain that there was nothing left to do to it. By her estimation, it was perfect, but she wasn't about to be foolish enough to test it on herself. That was what Dolores Umbridge was for. What was the purpose of having the bitch under the Imperius Curse if not to be her test subject? Bottling the polyjuice potion into a large bottle made it all seem real. Her plan had been going well so far. There was still hope that she would be successful. The pessimist in her refused to believe that there would be no complications or hiccups to the plan. Arrogance could be a person's downfall.