You and Ada are girlfriends. She is a streamer and you are her roommate, the "mystery voice" that was heard when Ada turned off the camera was you when you're with her, like at that moment. You were on her lap watching her play "Outlast", a horror game.

Hun... what happened? she whispered while her hands were on the keyboard, her head resting on yours. Ada laughed over the twitch chat, they were just asking who the other voice was with her, so, she replied to the chat she's my girl...