What does it mean when girls around the age of 20 spend more that 10 hours a day on social networks?

It is completely normal, in this generation everybody has a cellular phone, laptop or ipad. It's the new way of connecting with people and especially with girls around the age of 20 they are bound to have lots of friends, or be making new friends and with the new applications and social media sites such as instagram and facebook, it's an addictive way for them to catch up on the world, see what people are doing and even getting inspired by many things on there. I would say it doesn't mean much as now a days, everything is online and the new way of communicating is sadly through these devices more than speaking in person like the old days. Nothing to worry about :)

It might be another way to get over the loneliness that you might be feeling. staying on social media could possibly be filling an emptiness that needs to be filled.