The downvotes are because of the title and the example (cause yeah; just tell her "no"). I had to read the post three times to find them, but there are good points in there. I feel bad for you.
Social health is important, and if you think something is wrong, then something is wrong. Absolutely don't waste the prime of your life being alone Look at your city events, find clubs, get a dog and meet people at the dog park, volunteer, go to the gym, go to a skate park.
But
social life ≠ social media*
The caveat* is group chats. Being excluded from a basketball pickup-games chat because of privacy has no easy answer: either compromise on privacy to improve social health, or be alone. That is something that's not brought up in privacy communities, and I think it's wise of you to see that problem and not be afraid to bring it up.
For the rest of the social media though, that's absolutely not the case. It's well documented social media always caused poor mental health, the companies know it's bad, and they spend billions trying to cover it up.
So if you change your stance on social media, just remember: Followers and internet points are a horrible substitute for friendship.
IMO it should be based on realizable net worth or income, whichever is greater. If someone is already in debt and has no income then it becomes a time cost (ex; defensive driving class) rather than a financial cost.