A person who posts things on social media, looking like she/he has the most awesome life ever, looking like she/he is very popular and/or looking like they're really hot. But in real life they are nothing more than a plain person, or even just a loser.
The social media faker can go pretty far with trying to look awesomer than they are in real life. things such as making fake accounts and using it following themselves, commenting and liking het posts, use certain like/follow apps that get them more likes and followers.
But also just changing their outer appearance by editing their pictures -too much- or talking like they're highclass

Noun: a friend who is usually only called upon by a friend when a more primary/prominent friend is unavailable.

Taken from the term “second string” in an athletic competition situation. In football, if the star quarterback gets injured during a play, the second string is called off the bench to replace him/her. A “Second String Friend” is essentially benched until needed, if ever.

Synonyms: Plan B, Second Choice, Secondary Friend, Benched Until Needed