I've heard an interview Halsey did where she said the song is about a lot people in her life. She felt like she was being taken advantage of and holding so much for others. Working on the song made her evaluate her relationships and cut people out, and G was one of them. But the song also opened a door for communication for them, which brought them back together.
The video is emotionally intense. I think a lot of us can find ourselves in Halsey's position one way or another.
Beautifully directed, credit to Colin Tilley for some incredible work.