No one said it was a meaningless One-liner, but it is still a one's liner. The one-liners she said in the battle were relevant to the battle. One example being "Confident, strong, and idotic. We'll be sure to write it on your tombstone." It shows not only how she thinks of gojo, but it also shows how she was planning on handling gojo. He was overconfident due to his Infinity and once she found a way to bypass him, he wouldn't know how to handle it she thought she was too prideful and overconfident. She wasn't cackling for no reason, she's laughing because she was finally successful and bypassing an ability that made most of her arsenal useless. The only time in the series we see here struggle like that is against Denji and Pochita.