"Th-... thank you, my friend. I don't know what came over me." They know precisely what came over them although perhaps not the terms associated with such an episode.
One moment, the bard had been enjoying the festivities, clapping along as a number of Mondstadters danced together amid music and drinks, and in the next someone set off fireworks far too close and far too unexpectedly to where Venti sat.
In a flash, the images before Venti's eyes transformed, laughing happy faces becoming those of friends long past, expressions frozen masks of rage or agony, staring unseeing up at the wind sprite. The fireworks' gunpowder had reeked of battlefield smoke, coating Venti's throat and threatening to choke them anew. Suddenly, they'd felt as small and helpless as the wisp they'd been born as, and in a panic, the bard toppled off the barrel they'd sat upon and made a stumbling escape.
Venti doesn't know if Vennessa had witnessed any or all of the instance; they only know that abruptly, she's there, catching them by the shoulders and easing their back against a wall. Her burning presence and the solidity of the stone wall grounds the anemo archon, scattered winds called back home as Venti's vision begins to clear. Still their heart pounds in thin chest, trembling from head to toe, but there is a small mercy in the phantoms of an ancient war no longer looming immediately before them, ushered back into the quieter recesses of their mind.
Weakly, but valiantly, Venti presents Vennessa with a watery smile. "I guess I had a little too much wine, huh? Haha... ha..."
No one needed to tell her outright that Venti sometimes wore their cheerful exterior like a mask, concealing their true emotions when they didn't wish to bog others down. The flippant rapscallion that others dismissed the Archon as masked old hurts and countless losses through the eons, carrying those burdens with a smile and a song to dissuade worry. But, as one of those people left who had lived through so much with them, as the pair had worked assiduously to reform Mondstadt from the plights the nobility had corrupted it with, she could tell when something was wrong in the bard. Drinking copiously was one thing, but the reaction to the fireworks had her worry overtly.
Thankfully, no one seemed to truly notice, too dazzled by the display to think much of the bard, and for once... Vennessa was grateful for it. Steadying him by the shoulders seemed to help, but it wasn't enough to simply laugh off.
"Venti." Without thinking twice, Vennessa enveloped them in an embrace; not so tight as to be suffocating, but anchoring enough that they wouldn't feel as though the ground would fall through at their feet. From the loud pop and sizzle of the fireworks, she could tell her friend wasn't well in their presence. Withdrawing from the hug, she linked their arms together and strode away from the raucous celebrations in favor of the nearby Cathedral that was thankfully nearby, most of the city amassed in the Cathedral's central square where the fireworks were being launched from.
"Do you want to talk about it?" she prompted gently once she had guided them to sit within one of the pews, the cathedral almost devoid of people but thankfully muffled the sound of the fireworks immensely.