OR she’ll be the one person in her grade without it, get isolated from social activity, and get detached from her friends. (Coming from first-hand experience of someone whose parents restricted them from video games and social media)
Well then, if everyone else is doing it!.. I don't buy it. People don't have friends based off of if they're on social media, or play specific video games. If they do, you don't want them as friends. It's the same reason I don't let my 3rd grade boy play FPS games even though he REAAALY wants to, and all his friends do. An 8 year old should not be running around in a realistic game shooting people. When his brain is more mature, he will have plenty of time to play such games.
Of course people have friends based on what their hobbies are. In my childhood and teenage years I was only allowed to play computer games during the weekend. While my friends were online chatting and gaming together, I was sitting alone in my room reading books and watching TV. That affected my social skills, the lack of which I still suffer greatly from. I'd be careful with denying kids things that are important in their social circles. The damage done by FPS games or other similar things is nowhere close to the damage done by social isolation.