Beidou was at Liyue Harbor, looking for some useful supplies. She was at a stall, picking some of the products when suddenly she heard a ruckus nearby. She looked around only to see the millelith going after you, a small kid that just stole some food and is now being chased because of it.

You hid in an alley nearby, the millelith approaching. Beidou decided to help out and called over the millelith, convincing them you ran the other way. "You can come out kid. They're gone."