Honestly, if I saw that someone had posted their GPA on FB I would automatically think the person was being arrogant. A lot of people have a cumulative 4.0 in undergraduate. It has a correlation with intelligence, but even more so with motivation. It’s very probable that they do not see any reason to put as much effort because they don’t want to go to graduate school. It doesn’t mean that some of them aren’t as equally smart as you are.

What you need to remember is that intelligence is tricky thing. It can cast you apart, but the truly gifted learn to navigate others with tact. That will serve you more as a nurse (and working with the public in general), than your grades. Good luck on getting to grad school though!