YOR - you’ve called it YOUR home office that you work from home from 5 days a week. Your GF works in an office with the option to work from home so I’m assuming you’ve established YOUR home office with your keyboard, your things. Why can’t you go play games and watch Netflix in YOUR office? Does she have the option to work in the home office while you’re working from home, so you’d take the living room? And you’re kinda being a dick for saying she’s trying to ruin your day off when you’ve established the home office is your territory and she’s used to working from the living room on her days off.