"Quick, quick, through the barrier," said Mrs. Weasley, who seemed a little flustered by this austere efficiency.
It had not escaped his notice that, despite Fudge’s assurances at their first meeting, they were now seeing rather a lot of each other, nor that Fudge was becoming more flustered with each visit.
Hermione looked flustered and immediately started fussing about for her copy of "Flesh-Eating Trees of the World" to find out the correct way to juice Snargaluff pods; Ron, on the other hand, looked sheepish but also rather pleased with himself.
There are no more uses of "fluster" in the book.
Show samples from other sources
He gets flustered when talking to groups and tends to lose his train of thought.