I created an app with share a file and watch it with someone https://github.com/LucCADORET/comeover . It works with WebTorrent (torrent for the web over WebRTC), has a wasm ffmpeg embedded for manipulatin the video file. I used it with my girlfriend a lot. I honestly couldn't tell you why I didn't use Discord directly though, as this is mostly obsolete now (unless for the quality of the video).