Board Thread:Speculation House/@comment-27404492-20170918133425/@comment-4010415-20170930025855

Nikoli the rebel wrote:

1) Window was closed

2) It was a writing failure. You correctly identified the intent of the scene. Yang definitely overheard Tai, Port, and Oobleck's conversation, and I'm not going to call it a writing failure, considering the fact that, while the camera was still in her bedroom, you can extremely clearly hear

Port: Thanks for having us over.

Taiyang: Any time. You're always welcome.

And that's why Yang walks over beside the window - because she can hear them, and she wanted to eavesdrop.

So, yeah, even though the window was closed, it's not like they had the camera immediately cut to outside and hoped that we would just assume Yang could hear them. They kept the camera in her bedroom at first in order to show us for absolute certainty that she really could hear them from her bedroom.