The last time Percy had seen Angelina was on Easter Sunday, when she had been invited to come to the Weasley family dinner by George... a strange action, considering what had happened between the pair of them at George's birthday party. As a result, Percy was not nearly as disturbed as Angelina seemed. In fact, he had dismissed the entire event in his mind as an unfortunate mistake.
"Hello, Angelina," he replied, and wondered why she was behaving so curt. Did George tell her something that colored her perception of him? Yes, that must be the reason, and so he reacted cordially, but not warmly. "Good to see you here."