Why is Ao Dai at the Chinese New Year event?

Ao Dai is a traditional Vietnamese costume, so why does Ao Dai exist at Chinese New Year events? Have you mistaken the china dress for ao dai? I need an explanation for this.

Ao Dai is a two-piece style, robe and trousers, and the robe is separated at the waist.
Cheongsam is a 1-piece style, robe, and the robe is separated at the bottom of the thigh.
The picture only has the upper body, so it is not certain that it is Ao Dai.

Rather than making sure that the costume is ao dai or cheongsam, It’s more important why that costume is called ao dai.