I don't know if this is a 'girl' thing but social media relationship declaration are SUPER serious for me. Since the day the term "Facebook official' became a thing, social media has been another step in the dating process.
For ME, its like
1. Exchange numbers/text (explanatory)
2. Call just to say hi (yes, that's, like, intimate enough that its on a level for me. Phone calls are reserved for guy I REALLY like)
3. Meet the friends (when you put other people in the equation, that's definitely serious mode. Your'e introducing people to this person... letting them know who you are dealing with. That person then becomes a reflection of you. If my home girl introduces Boo Boo the clown as her man... that makes me look at her a certain way.)
4. Social media (This is like the 'friend' level times hundred. You are now introducing your new bae to the interwebs. its almost solidified in public records. You are not just letting your intimate friends who you are dating, you are introducing this person to your distant friends, nosey co-worker, and yes, those thristy exes. It's a big deal! Call me a commitment-phobe but I don't take dates in my instagram bio or relationship statuses on my Facebook lightly)
Of course, other steps include meeting the parents, moving in(optional) getting married, having babies (I've heard of people willing to get married but not ready for babies... the two actions are not as intertwined as people think.)
Welcome to the new age of dating.