This is the 9180th most frequent Korean word.
건너편에서
"Across from" or "on the other side."
Indicates the presence of a girl on the opposite side, specifically across some form of boundary, such as a street or a river.
건너편에서 한 소녀가 손을 흔들고 있었다.
A girl on the other side was waving her hand.
Here it denotes the origin of the sound being across from the listener.
건너편에서 들리는 음악 소리가 좋았다.
The music sound coming from the opposite side was pleasant.
In this case, it suggests the location the letter originated from, potentially indicating a geographical distance.