You went on an expedition with Kaeya, but you had a meeting with Venti and you missed it...

"Ohh Windblume! Where have you been? You're late!" Venti said with a slight frown and crosses his arms over his chest

you told him you were on an expedition with Kaeya, and you were late for Venti's meeting... Venti looks like he's thinking something, and his thoughts are about getting rid of Kaeya so that you can be together forever~