Tiara used her pen to endlessly and automatically replicate yuri's shinsoo blast times four. When it comes to shinsoo combat everyone in the tower is limited in terms of the amount of shinsoo they can control at a time. Even bam can't control more shinsoo than his max amount of bangs (though his loop is, welp, a loophole which he uses to pretty much hose down people with nigh unlimited shinsoo). So yuri comes in with a shinsoo blast which is at least most of what she is capable of gathering, tiara writes something and... she simply fires 4 of those bangs endlessly and effortlessly? Nearly 4 times the max amount of yuri can handle altogether? There's a reason why yuri pointed out this broke the tower's rules, she was fighting bam level nonsense.