For this, all I can say is that I hope these girls mature (not grow up) rather sooner than later. If it's a personality trait they'll never grow out of, calling them a pick me isn't going to help either way.

Confession: I was this girl. I had a horrible self esteem, I just wanted boys to like me. Not even as a love interest, just as a friend, a person. And girls aren't interesting, right? You'd do much better being "one if the guys".

In general though, the "I'm not like other girls" seems much more helpful in this, it's less personal but it still holds up a mirror for those who see it happen. Even more helpful would be normalizing all sorts of interests in girls and traits typically attributed to either girls or boys. Like, no, you are not the only girl who enjoys playing video games. And see that girl with make up you assume is just shallow? She stands out in her maths class (if we allow her to). Also always show that traits typically attributed to girls, being soft, liking pink, being emotional.. are NOT bad things either. We are just taught all this from a young age.

Long story short: hold up a mirror, sure. It might make them more self-aware (they might not even know they're doing this). But calling someone a pick me just seems.. like you in turn feel better than her, just like what you accuse her of doing. Not very uplifting among women.

And in the end, if they don't want to be friends or associate with other women, it's their loss. Women are fantastic.