The guy here goes by the name Reeflay, and this woman, Valentina, was possibly his girlfriend but could have been just some other woman. She was also a streamer, and after getting into a fight with Reeflay, his stream went silent for several hours, then restarted with her dead body on his couch.
According to a Russian news site, Valentina was pregnant at the time and may have been abusing prescription pills as well as alcohol.
When Reeflay woke up in the morning, he found Valentina's body and called emergency services, who pronounced her dead.
Some fans apparently believe this whole thing is an act to get attention, as this guy has a history of pulling pranks online. Disbelievers claim the death was faked and the EMT was a hired actor, but since this is happening in Russia, we can't go there to verify.
Anyway, the next time anyone asks what happens on Twitch, you can say it's the place where people die on livestream.